The main issue is GNOME, really. They are keen to pare down the functionality offered to users and app developers, and so will block standardization of extensio

The main issue is GNOME, really. They are keen to pare down the functionality offered to users and app developers, and so will block standardization of extensions that try to bring wayland up to feature parity, and even if they do get standardised, they will refuse to implement it. Which basically means many developers and users don't want to play ball with wayland at all, and the network effects are fairly strong (devs will not bother with the effort of making something work as best it can on wayland if users still happy to use X11, and users won't switch to wayland if their apps don't work or work less well). (Why does GNOME still matter? They've got the most developer resources of basically any group in the linux desktop space, and a large part of the market share because they're the default on a few of the larger distros)