The animation doesn't really bother me, as such, though yes, the transitions are hellish slow. I just loathe fullscreen. Having 2 27" screens makes it the most useless "feature" of all time. Random Space 'numbers', no spread over both screens [if you fullscreen any app the other screen goes black, & no, I am not going to ever use 'screens have separate spaces, that's even more irritating]… it's just a bad idea, made badly.
The only reason I see it having any use whatsoever is if you're stuck on a laptop with a teensy screen & trying to make the best of what screen area you have.