And this transition is nowhere near done. Just look at Kicad and pretty much any DAW that loads audio plugins (to name two major usecases where Wayland simply doesn't cut it).
Sure Xwayland exists and mostly (not entirely) works, but that's a band-aid for what is essentially a "we broke it and don't care" approach.
The daw problem is really really bad too. We've got a de facto standard forming right now where you link libwayland.so and hope the structs never ever ever change in the next 30 years.
Also, as benchmarks show, xwayland introduces pretty bad latency..
The latency isn't that bad, it's reasonable for a compatibility shim.