ssh -Y will work find on a LAN, but higher latency links are a really bad experience; X11 is a very chatty protocol with a lot of round-trip delays. On top of that, you cannot detach from such sessions. If e.g. your ssh connection gets reset, you lose any unsaved work in the program.

Traditional VNC servers allow detachable sessions, but the local use is kind of crummy.

Tools like x11vnc are closer, but they lack options to lock the display on the local machine, which is something remote desktop has done by default since at least windows 2000.

Yes, I can see that. It certainly isn't ideal and I wouldn't do something crazy like running a web service based on this technology. However at least within a LAN it's good enough and I wouldn't want to loose this capability for the sake of 'moving with the times' (wayland).