There are, in practice, 3 that anyone cares about - GNOME’s, KDE’s, and wlroots. I don’t know how much of their work is potentially portable across the three.

But while most users are currently on Xorg, the work going into improving responsiveness and suchlike is all going into Wayland. This project is really putting lipstick on a pig.

Also, compositors don't really need much improvement in this area, everything has been done ages ago.

It's all about the toolkits, and some great work is happening in GTK, e.g.:

https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/1562 https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/1117