It works, it's just kinda big for a lot of things. If someone's making good use of the engine's extensive features then that's not a problem, but it's a bit too heavy for a lot of simpler (previously flash) games. To be fair though, flash was insanely cumbersome and dreadful to deal with, and people still used it, so I'm sure they'd put up with WASM Unity even for those sorts of cases.