It's annoying, X got to the level where it "just works" out of the box for me on my setup and now it's "well, fuck that, we got bored, let's go Wayland!"
And some design decisions are.... iffy at best. Like the fact now every DM have to implement its own mouse(trackpad etc.) management coz "well we don't wanna" (basically, I'm sure Wayland developers have better articulated response to why everyone else involved have to duplicate the code).
Or how many hoops software have to jump just to record screen (or is that fixed now?)
Shared code can (and does) exists outside of the compositor or display server protocol. E.g. for your ending question xdg-desktop-portal is the shared resource in use these days.
I think the biggest mistake of Wayland was the rush on early migration for general use before it really had time to soak. The general design and not having everything in the display server itself is perfectly fine.
1 reason I can think is kinda the same thing with Vulkan. They both are so agnostic to what they run on that they have a minimal set of things that they function with.
In the case of Vulkan its: I interact with the graphics processor, and don't care if you have a display so windowing is an extension and has platform implementations if applicable.
And in the case of Wayland its: I am a protocol for managing and displaying windows, and I don't care what kinda inputs you have (example: VR doesn't have classical PC inputs).
And some design decisions are.... iffy at best. Like the fact now every DM have to implement its own mouse(trackpad etc.) management coz "well we don't wanna" (basically, I'm sure Wayland developers have better articulated response to why everyone else involved have to duplicate the code).
Or how many hoops software have to jump just to record screen (or is that fixed now?)