The worst fucking design failure of the unmitigated disaster that is Wayland is that "should I replace an X11 backend with a Wayland backend" is even a question worth asking.
Xlib is terrible! Nobody sane would ever want to code against that trainwreck of an API. It would have been so easy for Wayland to sweep in like the fucking Rohirrim and kill Xlib once and for all.
They *just* had to provide a feature complete replacement for X11 with a saner API. Complete failure on both accounts >:(