When Wayland was proposed, it’s biggest benefit was for direct rendering. At the time AIGLX was still the main hack to getting decent compositing/GL performance and had some major drawbacks. Wayland was designed in a manner more similar to the DRs in other desktop OSes (Windows and OS X, primarily). But, in its long development and adoption period, X’s DRI/DRM infrastructure has had plenty of time to mature and many of those arguments have been made moot. In fact, it still generally outperforms Wayland in many cases:
https://www.phoronix.com/review/nvidia-510-wayland/2
Theoretically Wayland is still conceptually superior in that regard; but you’re right, it hasn’t shown the drastic improvement originally promised.