I think as funny/cute mini-stories on their own, the Disney Worlds are fine because they play with the original properties and the Kingdom Hearts original stuff in fun ways. He's not wrong about the Disney part of the game being totally disconnected from the actual KH3 story that is being told though. Every world was just a wild goose chase for everyone involved, and they don't matter at all.
New Seven Hearts?
Black Box?
The nature of hearts in inanimate objects?
Negative emotions as a power source?
All interesting ideas that seem like they're leading to something towards the climax, but really, none of them mattered. They were all red herrings. The only thing that mattered was Sora realizing that NONE of that mattered and the power was within himself all along.
I mean, none of them matter in the long run because Xehanort is always 18 steps ahead of anyone which kinda makes him a bad antagonist, but they at least bother to explain what the heck they're doing there this time.
New Seven Hearts was them pushing Sora to keep building up his seven because they had alternatives if he didn't deliver - it's basically the only tension the story has until the finale. It also shows that they can manipulate a lot of stuff behind the scenes. In Arendelle, they point out that they were able to find two new princesses specifically because of what they did by manipulating Hans's darkness.
Hearts in inanimate objects ties directly into the whole replica deal, and it's a loose explanation about how Xehanort is able to take over people as well as bring his past selves back in some way
Negative emotions as power was just a way to tie Vanitas into the story admittedly, but there's at least a scene about how he wanted to use the factory to fill the worlds with unversed. I'll concede that they payoff there is kinda weak, but it makes some sense why he'd seek the place out.
The only thing that's really left dangling is the Black Box, and we already knew that there wasn't going to be a payoff until 4.
I think the real issue is that we all forget that KH is really never anything more than a series of vignettes and the main arc is only ever an excuse to visit the Disney worlds for whatever reason (find the princesses of heart, find Kairi and Riku, hunt down a bunch of guys in black cloaks). If we ever remove that from the equation, we've got about 5 hours of nonsense with basically no tension, since nothing happens in any of the original worlds either except set up the reason they're exploring Disney worlds in the first place.
