For me the biggest issue with X is that it can’t do per-display scaling, which makes it pretty annoying to use with one 4k and one 1080p display.
The only workaround that I’ve found so far that sorta works is just scaling everything up to where it looks good on the biggest screen, and then scaling the other screens down using xrandr.
Then again the only reason I haven’t committed to Wayland is because the issues I’ve had there have been much worse.