How long have you been using each of them? In my years-long experience it's been the exact opposite. Manjaro goes out of its way to not break anything and offers safety measures out of the box to recover if something should break. Arch doesn't care, it introduces breaking changes all the time and expects its users to be able to cope with them.
They target very different types of users and have very different goals. Manjaro explicitly tries to be stable and user-friendly whereas Arch exclusively caters to advanced users and aims to be customizable above all.
You can achieve the same with Arch that you get out of the box with Manjaro but it's not there by default – because that's not something a lot of Arch users are seeking.
For a normal user, you probably won't notice that technically manjaro is not arch and EOS is.
What's a "normal" user? On Linux you get all sorts. But you will most definitely notice a difference between daily driving Manjaro vs driving Arch.
Manjaro uses the binary packages prepared by Arch but a distro is more than just a set of packages. (In fact a distro should be more than just copying packages, otherwise it wouldn't be worth being called a distinct distro.)
Arch's goal is to be an ultra-customizable distro. To this end it starts out extremely minimalistic and requires the user to "assemble" it during the install from basic components, just so it doesn't end up with anything that's not wanted.
If a user can do this then they're above average in experience and knowledge; and since Arch can reliably assume this about its users it doesn't coddle them. The maintainers can afford to issue breaking changes that may even go as far as render your install non-operational, because they know their users can deal with it.
Another big Arch feature is being a rolling-release distro and bleeding-edge. This means that packages are released as fast as their developers can make them. This means they often have new bugs. This is the price users pay for the privilege of having very fresh software all the time.
Manjaro prioritizes a safe environment for the user and a more stable experience, where the install doesn't break (at all, if possible), and can be very easily be restored if it should break. And as a consequence it attracts users with less experience and Linux knowledge.
However, in order to achieve this Manjaro does some things very differently from Arch:
It holds back new packages and releases them late(r), when the Manjaro curators deem them usable.
It offers an alternate package manager with a more user-friendly interface.
It recommends the use of long term stable kernel (LTS) releases and mandates installing crucial drivers (graphical drivers in particular) through its own custom tools.
These differences mean that if a Manjaro user were to ask for help from an Arch crowd, the Arch users can't reliably help because they have no idea what's going on on the Manjaro side. They may use older packages and the issue being described was fixed in a very fresh version. They use tools (the kernel manager, the package manager, the driver manager) that Arch doesn't have.
Also there's very little overlap between the average Manjaro and Arch userbase. If an Arch user is more experienced and the Manjaro user isn't they're going to have trouble relating to each other. The Arch user doesn't see an issue in some occasional breakage, whereas a Manjaro user might consider that unacceptable and so on.
Last but not least there's a purely technical reason – Manjaro not only delays packages but hosts them in their own repositories, and sometimes goes as far as changing them. This makes it literally "not Arch" – using distinct repos is a step too far in terms of distro heritage.
Thank you for the very detailed explanation! Makes sense now. I was of the mindset that Manjaro is an Arch derivative making it technically Arch and didn't really take the repos etc into account. Makes sense why they advise against the use of AUR
You've opened my eyes haha.
I appreciate the response, I always worry asking "noob" questions from all the elitist horror stories you hear around Linux
The repo delay is not the main cause of AUR warnings. While it can in theory cause mismatched dependencies for some AUR packages, in practice it doesn't really happen that often.
The main issue with AUR is that it's completely unregulated. Anybody can put anything in it, there's no quality criteria, AUR scripts run as root and can do anything on your system, 75% of AUR packages were not updated during the last year, 15% were released once and never updated, and 10% are completely abandoned.
Arch itself doesn't support AUR for those reasons. You should be wary of using AUR packages in general, on any system that can use them, always assume they can break at any moment, and never use them for anything critical.
As an example though, I use the AUR for the arr packages. If not from the AUR, where else would I get them? Would I need to clone the git and build them myself instead?