@erincandescent @dalias @mcc @whitequark @becomethewaifu yes, you just need to completely rewrite all of your window management code in a way that is different from how every other OS implements it. Which is a huge headache.
More fundamentally though... wayland released without xdg-toplevel-drag, this is a fairly recent addition.
My biggest problem is that it's being rolled out prematurely, there's still things it can't do that X11 can, and distros should not have been making it default until much further in the future when things were stable and generally at feature parity.