How long ago was this written? Sure it's not perfect but you can run a lot of distributions like fedora, ubuntu, opensuse etc etc whatever exactly as described. Maybe this is a joke I didn't understand lol. But in case it is not:
No need to use command line if you don't want to
Drivers are installed automatically (okay this might depend on the distro but in OpenSUSE I recall this being possible in a GUI)
There is a steam flatpak, and most user apps can be installed through a GUI, often as flatpaks
For a user like this, I see no reason to interact with system packages other than choosing when to update.
I'm a programmer and even I rarely edit ANYTHING in /etc on my desktop. Sure I edit stuff in ~/.config, but that is not stuff a "normal" user would need to do.
Now sure if you want to start customizing your login screen and this that and the other thing, eventually you will have to run something on the command line. But Windows doesn't allow much customization beyond changing your desktop background, and pales in comparison to the amount of customization you can do with KDE, all through a GUI
What you're saying is correct but all the things you're describing are not 100% foolproof. Flatpaks are community maintained and can contain misconfigurations.
Also the sandboxed nature and all these foreign concepts for new users would have a user question why they're not seeing their folders or why their cursor or theme doesn't match their system.
These systems are great but they're not nearly as polished as Windows and Mac.
It's great for us but Linux has always struggled with any semblance of full polish. I think you're overestimating the average computer user. Probably Ubuntu based distro's are still as close as we got to an OS for the regular person.
The introduction of new concept could be mitigated by a proper system of introducing and explaining these to a new user but it's difficult not to overwhelm them with info or keep them engaged and willing to learn.
I got into IT because troubleshooting Windows gave me a lot of experience. I don't think there is anything that comes to mind that would make apps less likely to have bugs then on Linux.
The only exception is gaming where a lot of game studios have years of experience with Windows APIs that they tightly integrated with in the past. Less needed now, but that's developer inertia for you.
I think the appstore / sandbox / flatpak situation is actually quite accessible to a younger audience that grew up with smartphones. They don't deal with files much
Not to mention the fact chromebooks exists where local files are a mere joke and everything get's uploaded to Google Disk or an alternative to that and they have never been more popular. The average person doesn't save a word-processing document on a computer locally, they save it on a cloud and trust whoever owns that cloud service.