To be perfectly honest Aerith had plenty of stupid moments in FF7R. If the questions is whether or not Kairi should have the sort of sarcastic happy go lucky nature that Aerith has I would say no.
Just because Kairi acted like a Tomboy in KH1 and a bit in KH2 doesn't mean her personality type transfers to what Aerith's is. I think a lot of people look at these characters and say "this character is more fun/lovable than this one so this character is better", but a good character isn't defined by a single good personality trait; however, unfortunately, in most of SE's new games that's how characters are written. It's fine to say Kairi doesn't have a personality, but that's less of an issue than the fact that her character's mood and personality don't fluctuate. It's fine to say Aerith has a fun personality, and a lot of people love her for that, but her personality stays there and as a result her characterization is just as flat as Kairi's.
Neither of the two character's are defined by what they like, their hopes, dreams, challenges, insecurities, etc... These things should define the characters rather than a singular personality trait. Comparing the personalities of characters in KH3 and FF7R is like comparing pokemon by natures. As if a jolly charmander is better than a neutral pikachu just because its jolly.
Anyway, I understand the question and I sympathize with it. Sorry for the rant, but I really don't think Kairi would be a better character or KH3 would be a better game just by changing her dialogue/personality