Comment by kelnos
> Wayland is far more modular.
Not sure I agree here, assuming you mean "... than X11". With Wayland, you put your display code, input-handling code, compositor code, session-handling code, and window-management code all in the same process. (Though there is a Wayland protocol being worked on to allow moving the WM bits out-of-process.)
With X11, display and input-handling are in the X server, and all those other functions can be in other processes, communicating over standard interfaces.
> you put your display code, input-handling code, compositor code, session-handling code, and window-management code all in the same process
That's an implementation detail. You can absolutely separate one out from the other and do IPC - it just doesn't make much sense to do so for most of these.
The only one where I see it making sense is the window manager, which can simply be an extension/plugin either in a scripting language or in wasm or whatever.