Not just that. It took major DEs a very long time to get to some level of readiness with Wayland (KDE is just getting to it). And some major applications aren't event close yet. Firefox seems to be in progress for years, and Wine didn't even start moving to Wayland, because of various difficulties.
One of the reasons why Wine worked in the first place is because GDI primitives map nicely to X11 drawing primitives. Wayland developers made the Yao Ming "bitch please" face and told us "no one uses those dusty old primitives anymore! Here, have a bare framebuffer and render everything yourself!"
I think that's less "hard" and more "impossible by design" - that is, Wayland intentionally doesn't give applications any way to know or control the absolute positions of their windows, and of course Windows applications expect this.
