40 years old is also what makes it so hard to replace or even reimplement. The bugs are all decade old features, everything is written specifically for Xorg, all of which needs to be emulated correctly. It sure did serve us well, it's impressive how long we've managed to make it work with technology well beyond the imagination of the engineers in the 80s.

There's this for the protocols: https://github.com/probonopd/wayland-x11-compat-protocols

It can be done, it's just nobody wants to do it. It's not really worth the effort, when you can work on making it work properly in Wayland instead. That way you don't need XWayland in the first place, but also XWayland can then implement it using the same public API everyone else does so it works on every compositor.

It's slowly happening. KDE can now do global Xwayland shortcuts, they also implemented XWaylandVideoBridge and compositor restart crash recovery for apps. We're getting proper HDR, we have proper per-monitor refresh rates and VRR, I can even hotplug GPUs. Some of that stuff works better in XWayland because we can just run multiple instances with different settings. For the particularly stubborn cases, there's rootful XWayland. X12 would have to break things too, and I doubt an Xorg rewrite would be all that much further than Wayland is. Canonical had a go at it too with Mir which was much less ambitious.

NVIDIA was right on that one indeed, but Wayland also predates Vulkan and was designed for GLES, pretty much at the tail end of big drivers and the beginning of explicit and low level APIs like Vulkan. They could very well have been right with EGLStream too, but graphics on Linux back then was, erm, bad. But in the end they're all still better than the kludge that is 3D in Xorg.

It's getting a lot of momentum and a lot of things are getting fixed lately. It went from unusable to "I can't believe it's not Xorg!" just this year for me. It's very nice when it works well. We'll get there.

I can't up-vote this enough. The "architectural purists" have made the migration a nightmare. Always blaming everyone else for simply not seeing their genius. I'm honestly surprised it's gotten as far as it has.