Well, I can continue on listing problems with X. How about HDPI? Or mixed HDPI? I’m sure some things can be retrofitted, but I still don’t see why should we continue with a protocol not planned for/with modern hardware in mind.

Also, regarding network transparency. As you note, most apps are no longer network transparent, and remote window streaming can be much better solved with modern compressions/encoding. It doesn’t have to be part of the core protocol, the latter should only concern itself with displaying rectangles on the screen. Everything else can be built on top of it.

Also, while in itself not a good argument, both MacOS and windows use a compositor since forever.