I don't like theirs either. "Realistic"/generic adult proportions just kill all the charm of the characters. Remove the heart cheeks and that could be any girl. Speaking of which, replacing Star's chubby cheeks with sharp cheekbones ought to be illegal. And their noses are weird, like they learned to draw with "tumblr nose" and are now consciously trying to avoid it and failing.
I don't like "aged up" art in general but there's definitely a way it can be done right.