I did find Sir Ian and Dame Judi a bit easier to look at simply because they have such extra head fur:I don't think there's necessarily anything wrong with the bodies of the cats (it's a little weird that they're plantigrade, and even weirder that Taylor Swift's cat is wearing sparkly shoes, but I mean overall). The heads are weird, though. Some extra fur/hair on the head wouldn't necessarily make them look more like actual cats, but it would bridge the gap between human and cat better.
I also realized there's potential for extra awfulness with Sir Ian, though: in the play, "Growltiger's Last Stand" is essentially a live-action flashback of Gus remembering his best role, and it's played by the same actor. If they put that number back in the movie, are they going to try to de-age Sir Ian as well as felinize him?!