Only thing I can remember right now reading about is that is is "not finished" and "not production ready".
I mean there is some truth in that because when I tried switching to it some months ago, it crashed in the first 5 minutes of using it. Haven't triey it since.
Others report using it all the time without any issues.
Basically there are a bunch of restrictions baked into Wayland that are there for security reasons. For example, the protocol doesn't have a way to record keystrokes. Which is reasonable since apps really shouldn't be able to do that whenever they want. But some apps really need that, and they had no way to. Recent extensions fixed most of these issues but it has been a long road.