The IME situation in modern X frankly sucks. Back in the day I regularly contributed to the relevant projects, but our efforts were continually thwarted by people who had no idea about CJK requirements and worse, won't listen to us ("why do you need to pass keystrokes to a separate process?", "users don't need a choice of IMEs per language", etc). It got so tiring that eventually most of the regular contributors moved on.

And now I have no idea what's going to happen with Wayland.