Amusingly, I often hear this argument from Wayland proponents. Do they realize, that those very same developers have failed at maintaining Xorg code base and fixing it's bugs in backward compatible way?
To run a project into the ground and wash one's hands of it... is not worthy of endorsement.
This may be a matter of different perspective, but from my point of view the Xorg maintainers did a monumental work modularizing and cleaning up the codebase. They kept integrating modern extensions and have kept X11 relevant all this time. Try something pre-Xorg to compare.
But to run a project into the ground and not wash one's hands of it is an even worse endorsement.
You might not trust the Xorg devs to develop you a new window system, but at least you'd trust them to know if their own, existing code has fundamental problems.
* this does not always work for other programs, and for Firefox you need to turn off bell events in about:config to avoid random crashes;
* (this may be upside depending on what your expectations are) X clipboard is still shared in the host->client direction.
X11 has some fundamental problems. It's not fun using a modern desktop where it is impossible to sandbox individual applications. Firefox frequently processes untrusted data and is run with a dedicated uid, but it is also an interactive application and can suddenly listen in on all my passwords entered in other applications. Virtualized appliations are referred to using dumber protocols like VNC and SPICE which isn't always ideal.
Wayland has some interesting design issues on its own but that doesn't make the developers ignorant. XWayland will stick around for the foreseeable future.