1. Their sample implementation was bad, I think it was just a demo app for car displays or some such. They should have ported over a simple wm.
2. Yeah, the major projects like gnome and kde had enough developers to dedicate to porting over to wayland. Most existing DEs and WMs found the porting process to be very difficult and didn't even bother. This would have been solved had they released an implementation with feature parity. See #1.
3/4. I don't care. I consider xorg to be 'feature complete'. There are few benefits to the end user switching to wayland beyond some niche use cases like multi-display scaling, and HDR. The small benefit of those is nowhere near worth the headache they forced on users when the major DEs started going wayland only.
Overall, I am happy sticking with xfce since it's taking the slow road on moving from xorg to wayland.