I only follow Linux graphics casually, but AIUI one of the principles of the Wayland initiative was to replace the monolithic model of X with a combination of m

I only follow Linux graphics casually, but AIUI one of the principles of the Wayland initiative was to replace the monolithic model of X with a combination of more tightly scoped components. For example, libinput was created to take responsibility for actually handling input devices, so that Wayland compositors would never need to carry that code, and the input device handling in X could be decommissioned. From that point of view, "Wayland" is kind of a short-hand for a number of different stacks that have some components in common, and speak the Wayland protocol. If you choose not to use a complete stack on a system, then the result can't be fully functional. Personally, I don't have any sense of how much dark matter is in the area of Linux GUI applications. We can easily know about Open Source, where most modern applications sit on toolkits and desktops that are moving to Wayland, but presumably places like CERN have some really old internal applications that will only ever run on X until they are replaced. I'm genuinely unsure how large that problem is. I have to say that I'm always skeptical about arguments that something can't be done for performance reasons. People have been using that argument against new technology since at least the days when C was decried as new-fangled, decadent luxury.