My understanding is that X was designed during the Terminal/MainFrame era of computing where window rendering, composition and display were distributed between

My understanding is that X was designed during the Terminal/MainFrame era of computing where window rendering, composition and display were distributed between the client and server which may or may not be the same machine. And that paradigm is maintained to this day in X which is limiting when all rendering, composition and display are handled locally and possibly offload to a GPU with the distinction between a client and server being unnecessary. So Windowing environments like Wayland have a distinct advantage over X when it comes to performance. I could be anywhere from completely right to utterly wrong on this so take it with a grain of salt.