I realise what I'm opening myself upto here when I say this, but all I expect from KH4 is a Ratatouille moment where I'm mentally transported back to KH2 when I watch the opening video.
Small, small, tiny winy, little expectations
i think this is very possible!! I don't mean to be reductive by saying this, but as someone who plays both games a lot, KH2 and KH3 are both games where Yen Sid tells Sora to go fuck around in Disney worlds, nothing happens, and then the plot happens at the end (and for a little bit in the middle in KH2's case). Neither of these games have ongoing important events that take place in Disney worlds, and even their endgames are mostly a sequence of unceremonious executions for the bad guys where some of the good guys reunite with Sora.
What puts KH2 ahead is that it has new characters, starts off in an unfamiliar setting, and introduces a threat that is (sort of) new to Sora. KH3 does the same story but lets it rock with all known characters, with the only fresh moment being Sora meeting Vanitas. KH4 should immediately feel more like KH2 with its new setting, villain roster, and slightly aged up(?) design for Sora.
I don't think they need to change too much about the established formula to make the game feel new, they just need to throw in some new stories, characters, and situations that feel unfamiliar to KH as we know it. These moments of unfamiliarity don't even need to make up an entire game, just exist alongside the more familiar side of KH as we know it in order to create a contrast.
As far as it 'feeling' how KH2 made us feel... a lot of that is just choosing how seriously we take this stuff. I'm going to invest in the game in earnest to the best of my ability, rather than point and laugh at the contrivances and occasionally embarrassing dialogue. But in order to do that, one needs to alter their thinking and expectations a bit. You can't go in expecting Shakespeare. I can pick apart KH's storytelling all day, every game not called KH1 is loaded with story moments that I consider to be unfathomably stupid, but sometimes its easier to just focus on the characters, the moments that DO work, and the whimsy. I'll only be harsh if I feel like NOTHING is working, which, luckily, hasn't happened yet in Kingdom Hearts.