Hard disagree. The morphing effects for Odo mostly looked pretty great.
I don't think they aged particularly well, but regardless, it was a very expensive digital effect for a mid-90s TV show, which is why they minimized Odo's shapeshifting considerably in the later seasons. Odo actually referenced that in some of the late episodes - that he he couldn't even remember the last time he had shifted.
Huh? Quasi is shown to assume other people’s appearance twice in the movie. Plus, there’s that scene where he turns himself into this tentacle being in that tunnel chase scene.
His skill as a shapeshifter is used for a bunch of dumb gags, not really anything plot relevant.
Well, the idea could be that she doesn’t have any “powers”. Kasquian holographic lifeforms could be bound to one appearance only.
I suppose this could be the case, but it seems like a pretty boring solution, TBH. Why have her be a holographic character versus say a synth in that case?