The work done in the 80s and 90s was for very different hardware than now, when accelerated graphics wasn't the norm. MS made that mandatory with Aero and then Windows 8 a long time ago, Apple's been at it for even longer.
Wayland exists because, thanks to hardware innovations, there's a better way to do the job than what was possible in the 80s.
We'd have had a lot fewer problems if Wayland had been X12, in the sense of taking an approach of gradual iteration, even if they went at it fairly aggressively.
E.g. instead of the Xwayland approach, you could've already ditched "half" of Xorg if you stripped most of the server-side drawing primitives and server-side font support and moved them to Xlib, handling it client side, and then made it clear someone else would need to take over maintenance of Xlib, and "started over" with a stripped down Xcb.
You could've validated further restrictions by letting clients opt in to them with extensions before "flipping the switch" and restricting them by default when the damage was acceptable.
Even if we then eventually reached a point where there'd be a schism, odds are it'd be far smaller. And certainly far less time would've been wasted.
Feel free to find volunteers to fulfill their shoes.