I mean, admittedly I'm also very biased. I just don't like Sora and Kairi as a couple because of the way it's executed just making it feel kinda forced from my perspective. That, and I personally just don't find it particularly interesting, even if I fully acknowledge it as a cute thing that a lot of people are going to love, and I am happy for those who got the SoKai content they wanted. I just feel that if they absolutely had to make it so blatant in KH3, it would've been nice if that wasn't all she'd basically been through the duration of the series. Idk, to me SoKai's just very much main guy x main girl, and I prefer more complex dynamics, like Riku's and Kairi's (and while I ABSOLUTELY ship RiKai, I 100% acknowledge it was never gonna happen. I just really was more endeared by his dedication to her in KH1 than I was Sora and Kairi's whole thing, so I wish their character dynamic wasn't left in the dust.]
It feels like the Destiny Islands trio only really matters in their relation to Sora nowadays. :/ The other trios are far more balanced. Terra/Aqua/Ven all care about each other and it's shown so clearly in BBS. Same with Roxas, Axel, and Xion.
In general, though, I just don't like when a female character has so little going on besides the love interest, y'know? We've seldom seen Kairi interact with... basically anyone else. We never got to see her time with Hayner, Pence, and Olette beyond a few seconds. Haven't gotten a lot of interaction with even Donald and Goofy. She had a few lines with Aqua, which was nice, but golly I wish we got more.
Which leads me to perhaps my one big issue with KH3: Did it really need to be Sora's story?
Think about it. Sora/Donald/Goofy are a huge, essential part of KH... but at this point, KH has had so many games with so many other main characters. I think if we had gotten some alternate routes for the others, then maybe characters like Kairi and Aqua would have been better realized in the scope of the story.
On the subject of Aqua...
Her jobbing so much still feels forced, even if it was due to her stubbornly pushing ahead. It just feels kiiinda like an excuse to not let her be the hero in a lot of cases? Keyblade wielders can still be competent with just raw magic- just look at Xion in Days before she gets a Keyblade! So Ansemnort beating her so easily just feels.... weird. At least make it a flashy fight where it feels like both sides are giving it their all, y'know?
And she didn't even use a barrier spell to block Vani's attack? I dunno. It just feels like Aqua got a downgrade specifically so Sora could be the hero.
I also truly feel Riku and Mickey should have been the ones to save her, since Riku has his whole darkness schtick and it would've felt more meaningful, but eh. I digress. The scene where she IS saved was still extremely wholesome and sweet, I just really feel that thematically Riku and Mickey would have been just fine.
Mind you, I do enjoy Sora as a character. He's fun, heartwarming, and SUPER important to the series. I just feel that he shouldn't be the fix to every problem.