Why Wayland adoption to have official support in programs is so slow?

Blender's Wayland support is not great because they're doing stuff from scratch. They're not using an existing toolkit like GTK, Qt, Electron, or even something like SDL to get Wayland support.
But if you're using an existing toolkit things are much easier and support is automatically there, you just need to do testing to ensure everything works.
The common biggest things that still use Xwayland are Chromium based apps and programs running under wine/proton. Chromium has an experimental Wayland mode that works well enough, but definitely has some bugs, especially around windowing. Wine Wayland is in the works.
- Thanks for the insight.
  Yeah Blender seems like an exception.
  Also that means I play lots of Wine/Proton games and many web apps / Electron don't care.
  
  Wine and Proton have actually put a ton of work into Wayland support, it's very far along. I wouldn't be surprised for Proton to have a native Wayland version soon.

You're asking the Linux community to agree on something
- No, he's not!
  
  Don't tell me what to agree with!
- Haha yeah but also to know something I'm missing.

for better and worse, XWayland works perhaps too well
- Not on Cosmic Epoch Alpha 1 but yeah 😆

Because it doesn't matter for most apps. XWayland works fine.
Even Blender says if it fails to use Wayland it will use X11.
What are you trying to say? Of course it does. Pretty much every Linux app still supports X11, because a lot of people are still using X11. Only exception I'm aware of is Waydroid.
- I believe Wayland should be the default, but we should have the option to switch to X11 (using XWayland on Wayland) if desired.
  
  Wayland is the default on blender, that is what that text says

good is the enemy of excellent. X11 works for most users (almost all the users?) well. You can see that with the adoptions of other standards like the C++ standards and IPV6 which can feel like forever.
Another thing I think one of the X11 maintainers mentioned iirc is that they have been fairly gentle with deprecation. some commercial company could have deprecated X11 and left you with a wayland session that is inferior in some ways.

Because Wayland is fundamentally very different from the older X protocol, and many programs don't even directly do X. They leverage libraries that do it for them. Those libraries are a huge part of the lag. Once GTK and Qt and the like start having a stable Wayland interface, you'll see a huge influx of support.
A big part of the slowness is why Wayland is a thing to begin with. X hid a lot of the display hardware from apps. Things like accessing 3d hardware had to be done with specialized display clients. This was because X is natively a remote display tool. You can use X to have your program show its display somewhere else. Wayland won't do that because that's not the point. Applications that care will have goals for change. Applications don't care will support it once someone else does it for them.
Right now, the only things that would benefit from Wayland are games and apps that make heavy use of certain types of hardware. Half of those don't care about linux, while the other half is OK with X and xwayland.

Also XWayland has many limitations as X11 does.
If an app has only ever supported X11, then it probably doesn't care about those limitations (the apps that do care probably already have a Wayland version). And if an app doesn't care about the extra stuff Wayland has to offer, then there's not really a reason to add the extra support burden of Wayland. As long as they work fine in XWayland, I think a lot of apps won't switch over until X11 support starts dropping from their toolkit, and they'll just go straight to Wayland-only.
- Yeah I agree. Maybe some day X11 will be seen as something legacy that needs to be deprecated. But not now...
  
  Plasma deprecated their X11 session in v6 pending removal in the future, and Redhat has already dropped it in Fedora & will do for EL in the next release.
  
  xwayland covers most use cases already anyway

Wayland does not work with screen readers like Odilia or Orca. Because Wayland leaves blind users behind, it's a total non-starter.
- True...
- Wayland "leaves blind users behind" due to its security oriented design. A protocol or portal of some kind is going to need to be created to solve this problem, but progress here is severely lacking.
- That's pretty shocking tbh
- Out of the loop, why is that ?
  
  Not an expert, not an insider. Just commenting to inform about what i know.
  When wayland was designed, security was a concern and it was handled differently than in X decades ago. That is good.
  Under X any application can be a screenreader and see your data. This was okay when you trusted everything on your machine, but is a problem today.
  Under wayland's original design, no application could be a screenreader. That's bad. It took way too long to agree on how to make exceptions to the rule, e.g. for screen readers, screen sharing in video calls, etc.
  
  Also out of the loop, but my guess is that Wayland hasn't defined a specific API for the purpose yet, and their security model doesn't allow programs to see the content of other programs' windows. X11 doesn't attempt to keep programs from seeing what other programs put on screen, so no specific API is needed there.

As someone who tries to look under the hood for a lot of the open source software I run, one thing that I have noticed is that there are a lot of cases where the general sentiment seems to be port to what. Wayland still doesn't support a number of things that some applications require. A lot of developers that I have interacted with would rather have the app run through XWayland rather than have a wayland version of the app with less features or certain features grayed out.
In the case of one project in paticular, that being the Sunshine game streaming project. I have personally witnessed. Them implementing a solution for wlroots based compositor. Having that solution eventually break as wlroots based projects deprecate the protocol they were using in favor of a new one and now that protocol is looking like it too is old news and is going to be deprecated in favor of a newer and better protocol. What I am getting at here is that protocols not existing isn't the only problem, but things are still very much in development. Even applications that implemented wayland support are being put in positions where they need yet another rewrite because things are far from finalized and still moving pretty fast.
- In the case of one project in paticular, that being the Sunshine game streaming project
  That's a terrible example, because they completely ignore the many many years old standardized APIs (screen casting and remote desktop portals) that they could use, in favor of doing hacky and broken things that require root access instead.
  
  Even then, is that a documentation and centralized standards issue? Was there some list they could have/should have looked to that said 'this is how that is implemented on Wayland vs X'?
- So summarizing Wayland is not ready yet for everyone and current Wayland support can easily be broken with newer releases?

It is not enough to make a better product.
It is not enough to create all tooling and libraries to seamlessly migrate to the new product, but it helps.
There also needs to be a great big positive reason to make the change. Paying developers, huge user base, the only hardware support, great visuals, etc.
Until I cannot run software on X11, I won't switch over knowingly.
- Once the desktops switch to Wayland and all distros ship with Wayland by default, support should slow.
  Ideally, developers stop improving xwayland over time and go into maintenance mode for a bit. Once it goes into maintenance mode, developers should naturally fall off as it winds down.
  If every desktop makes a very public announcement about the xwayland protocol being put into maintenance mode, actively supported apps should switch over. It's up to the public how long they want to keep maintaining xwayland (open source etc).
  
  So, even though KDE Plasma has significantly advanced Wayland, a stronger push is still needed to drive the change further.
  
  xwayland cannot ever be removed, because wayland, by design, will not have enough functionality to replace it. So one can either support X desktop environments with their own individual bugs, or one X implementation that has the needed features and works consistently for all DEs
  
  But why would the distros do that? It takes effort and has real costs for them.
- Until I cannot run software on X11, I won't switch over knowingly.
  Please explain
  
  Most people use their os to run their programs. So if their programs don't work without x11 people won't switch.
  
  What is there to explain?
  Please explain.

Because Wayland is STILL lacking a lot of things that people need.
- It's the opposite for me. X11 is unusable on my laptop because it doesn't support fractional scaling well, whereas on my desktop it doesn't allow for a multi monitor setup with different refresh rates. Both dealbreakers are not present with Wayland. Though your point still stands; NVIDIA GPUs continue to suck more with Wayland than X11 for example.
  
  I'm not defending x11, both wayland and x11 are trash, it's just whichever trash pile you find yourself most comfortable in.
  On x11, fractional scaling is more or less just handled by the gui toolkit. It does suck that you need to set an env var for it, but IMO that isn't too bad.
  the multi monitor stuff does suck for sure. It's not an issue for me personally. One thing that is a massive issue for me is x11's terrible handling of touch, I use touch screens daily so that's a massive issue for me, wayland compositors are also typically quite a bit faster then x11 + wms on low end systems now too (not to be confused with total resource usage/lightness).
  Wayland has a lot of things going for it, but it also has a lot going against it. Both are terrible. Arcan save us (oh how a man can dream)
- Could you give me some examples so I can understand what's missing and being waited on?
  
  Someone above mentioned screen reader support for blind use accessibility stuff. For users who are blind, this is critical.
  
  for one, it's missing a good chunk of A11y stuff, activity watch requires something to monitor the active window, there is a PR for that, still not merged, this has been an issue for years
  It's missing protocols that will let applications request to be a privileged application, which is necessary for applications to use other functionality.
  Missing protocols to control always-on-top / layers, which is needed for OSKs to function, and a couple other A11y things off the top of my head.
  It's not just a11y either, Window positioning still isn't merged, which means if your app opens two "windows", you cannot currently select where to open them, or to even bind two windows together (Android emulator does this for instance).
  There is a LOT wayland is missing, it IS getting better, just at a snails pace.

Wayland for better or for worse is still in development, it's actively changing and a lot of developers can't (or don't wanna bother) keeping up...

In my opinion, that's because X11 lacks proper abstract for many things like screenshot, screencast, color managerment and etc, so the applications have to use many X11 implementation details to implement these features. It leads to high-coupling code with X11 so move their code to wayland and ensuring it works correctly and is consistent with the old behavior is difficult.

Until recently, Wayland development was rather slow, especially in the areas where more specialized software run into issues that force them to stick with X11. Since Wayland does a lot less than X11 and is more componetized across multiple libraries designed to be swappable, some of these areas simply do not have solutions. Yet.
And, as always with FOSS, funding is a big part of the problem. The recent funding boosts the GNOME foundation received have also led to some increased funding for work on Wayland and friends. In particular, accessibility has been almost nonexistent on Wayland, so that also means that if an app wants to ensure certain levels of accessibility, they can't switch to Wayland. GNOME's Newton effort is still very alpha, but promising.
While big apps like blender and krita get good funding, they can't necessarily solve the problem themselves by throwing money at it, either. But the more funding Wayland gets to fill in the feature-gaps and ease adoption, the sooner we'll be able to move away from xwayland as a fallback.
Wayland and its whole implementation process certinally aren't without fault. There's a lot of really justified anger and frustration all around. Even so, staying on X11 isnt a solution.

So software like CAD is funny. Under the surface, 3d CAD like FreeCAD or Blender is taking vertices and placing them in a Cartesian space (X/Y/Z - planes). Then it is building objects in that space by calculating the mathematical relationships in serial. So each feature you add involves adding math problems to a tree. Each feature on the tree is linearly built and relies on the previously calculated math.
Editing any changes up tree is a massive issue called the topological naming problem. All CAD has this issue and all fixes are hacks and patches that are incomplete solutions, (it has to do with π and rounding floating point at every stage of the math).
Now, this is only the beginning. Assemblies are made of parts that each have their own Cartesian coordinate planes. Often, individual parts have features that are referencing other parts in a live relationship where a change in part A also changes part B.
Now imagine modeling a whole car, a game world, a movie set, or a skyscraper. The assemblies get quite large depending on what you're working on. Just an entire 3d printer modeled in FreeCAD was more than my last computer could handle.
Most advanced CAD needs to get to the level of hardware integration where generalizations made for something like Wayland simply are not sufficient. Like your default CPU scheduler, (CFS on Linux) is setup to maximize throughput at all costs. For CAD, this is not optimal. The process niceness may be enough in most cases, but there may be times when true CPU set isolation is needed to prevent anything interrupting the math as it renders. How this is split and managed with a GPU may be important too.
I barely know enough to say this much. When I was pushing my last computer too far with FreeCAD, optimising the CPU scheduler stopped a crashing problem and extended my use slightly, but was not worth much. I really needed a better computer. However looking into the issue deeply was interesting. It revealed how CAD is a solid outlier workflow that is extremely demanding and very different from the rest of the computer where user experience is the focus.
- It's true what you write, but it's not related to Wayland/X11.
  But this is the reason CAD software can't use multiple cpu cores for geometry calculations. The next calculation needs the result of the previous one, it can't be parallelized.
- Wayland will perform better than X as there is no server it has to go through. It can talk almost directly to hardware
- Yet games like Dyson Sphere project a triangle grid on a globe, run fine in wine wayland?

Wayland isn't even adopted by every desktop environment yet. xfce, cinnamon, mate, lxqt, and all the ancient window managers all use x11, and all have their users.
If it works on xwayland, chances are it won't be switched for a long time.
- Xfce4 and cinnamon are close to wayland support.

I heard wayland is hard to develop for and xwayland work a little too well, idk I'm not a programmer
- I think X11 works out of the box but Wayland needs more knowledge and effort for now.

As a disclaimer: I really like Wayland and use it as my daily driver for months now with KDE/Proton.
Now my answer, based on my best knowledge:
Because there is no real Wayland to implement, the base Wayland protocols are extremely bare bone and most of the heavy lifting is done by all the different wayland compositors like hyprland, plasma, Mutter, weston, wlroots, gamescope so as a developer you don't have one target to program against (X11) but lots of different wayland implementations and those are not always doing things the same way or providing the identical interfaces/API or have the same level of features.
On my system is at least one wayland only program that works absolutely fine when started in a wlroots environment but crashes (reproduceable on different systems) with a segmentation fault in Mutter or Plasma.

Some applications, such as those with tablet demands, are not met by current wayland des with proper tablet support and xwayland is currently the better option. This may have changed in the last year or so, but this is roughly my recollection of certain big art programs.
- Xwayland doesn't get input in some special way, it uses the exact same Wayland protocols to get input events as native Wayland apps. All claims about it being more complete or anything like that are nonsense.
  Krita forces Xwayland because they have some X11 specific code they haven't bothered porting away from, that's all.
  
  Oh hey, I love your work on Plasma's HDR and color management. Glad to see you on Lemmy.
- Some many specific issues with Wayland... Maybe that's a reason. X11 is a huggeee dependency for a long time.

May programs do though
- Minority rather than majority.

because for most of them, there is nothing to port them to. Wayland is incomplete... by design.
- What are advantages of being
  incomplete... by design ?
  I know Wayland is simpler but it should cover almost every highly requested feature if developers need it.
  
  "almost" being the key word there.

It is still young and underdeveloped.
It is advertised to be simpler, but I don't understand any of this words thrown in this thread. And I don't care. Pulseaudio and pipewire is still making me troubles, even thou alsa worked without issues for me.
Point it, make it clear and stable and we will come. Until than we will use the beast we know. It os mich easier when there are no options, but Wayland is fighting something that exists and it takes time and effort.
Another problem is they pushed it to early and people got burned. Until I start seeing "I switched to Wayland in one command and everything works" I (as a user) will not touch it (unles my distro decides to drop X).

Because it’s so complicated that given a page (page and a half) to answer the simple question, “Why does Wayland support still give you more problems than solutions?” We had to describe it like the summary of a PHD theses in client server architecture?
Come on with that load of hot trash 😭
- Do you want the short answer? The short answer is "Because there's a lot of applications that do a lot of different things and getting a good design for a protocol that supports all of those things is a process that takes time"
  
  With the headline, yeah… kinda :-) Your answer plus a bit of “this is why it’s important.” And I would have grunted and gone back under my bridge…
  I’m feeling a bit sheepish about my comment on the other side of the day.
  But I was also hoping for a lot more. Better desktop security… and that’s underselling it because my understanding is we’re pretty much coming from zero, so this was always going to be rough.
  I have yet to run into an insurmountable issue, but I’ve just hopped distros rather than (successful) troubleshooting. Always makes me grumpy ;-)