It's important to know that there were once many implementations of X11. Xorg is the only one that hasn't failed. Everything else is unmaintained now.

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.