Wayland was specifically built to support things that aren't desktops, so feature parity with X was never a design goal of Wayland. The idea was that Wayland would be a super-flexible "you give me a window and events, I give you rendered bitmaps" kind of protocol, and then desktop functionality would be layered on top for people who wanted a desktop. Not everything needs to be a desktop (e.g. car infotainment displays, KDE Plasma widgets, etc), and some protocols would be super limited if they had to fit in a desktop mold (e.g. VR displays[0] with apps in non-planar windows).

The main mistake FD.o made is that they didn't get consensus on a "Desktop Profile" extension, so all the DEs wound up implementing their own thing. This is still fixable, just very annoying until we have agreement on this shit. I think that's what you meant by "feature parity with X".

[0] Currently, every desktop VR setup has to have two layers of compositors. VR applications have to communicate with a special VR compositor that then draws normal desktop windows with the contents of what should be hitting each eye of the VR display, all so it can pretend to be two normal displays.

I could say the exact same thing about X, A lot of the problems people had with X historically was that developments goal was to "create mechanisms not policy" and people just wanted a desktop environment that worked.

An antidote on non desktop use of X: the other day I wanted to show a program on my phone, there are many good ways to do this, but I picked none of them. Instead I had just installed a terminal on the phone and noticed they had an X11 package, So A few minutes later I was the proud owner of an X server on a phone. And you know what... It was pretty great. My gaming system load and temps dashboard were displaying just fine.

Despite using X for many, many years, I had never just sat down and played with a bare X server, I had only dealt with it through the lens of a locked down, encumbered desktop system. It was like having a network attached monitor. From whatever system I was using as a desktop system I could just go "display this on that monitor", in this case a phone. Based on that experience I put a raspberry pi on my TV running a bare unprotected X server because having a network attached monitor rocks.

Yeah, pretty much. I would be less disagreeable about Wayland if they had solved this problem early (and yes, they should've thought about this early during Wayland because the most prominent target is desktop environments). But they didn't, and I don't even know if they'll come up with some unified solution that all DEs/WMs can agree on or whether they'll just keep allowing DEs/WMs to do their own thing. Either way, fragmentation is never a good idea on what, I think, many would consider critical functionality. At least, I consider the requirements to implement accessibility to be rather critical, which is the primary reason I still use Xorg.