Then the problem is that it’s abandoned, not that it has stagnated
By all means, feel free to start working on it!
All the people who developed Xorg for 20+ years decided that creating and working on Wayland was a better use of their time. But I’m sure you know better…
The problem isn’t that Xorg is spaghetti code (it’s pretty good for a large C project, imho). The problem is that the X11 protocol was designed to expose the capabilities of 1980s display hardware.