You don't have to put down KH2 to talk up KH3 and also that's just flat out not true. With the sheer number of disney worlds KH2 had there are a few duds but there are plenty that relate/forward the main story.
Lemme remind ya that the second half of KH2 only exists because SDG didn't go straight to Twilight Town after being given the box with the ice cream and photo.
Out of the entire second half we only got
The conclusion of the Xaldin thing
Riku and Xigbar[for five seconds] with Xigbar apparently turning a dragon into a heartless off screen.
The rest is "Oh no we gotta stop hades' tournament"
"Oh no we gotta stop Jafar"
"Oh no we gotta stop Scar's ghost"
"Oh no we gotta CATCH THE GIFT THIEF"
"O H N O U R S U L A"
"We gotta save Hollow Bastion again[best revisit imo]"
Like, the realistic course of events would be they get the photo and head to Twilight Town.
But they don't and the excuse for the revisits that is only mentioned in Beast's Castle IIRC is that they're looking for a way to the TWTNW.
If you wanted to you, with a little finnese you could just merge the first and second visits together.
Hot take: KH2's midpoint from the invasion of Hollow Bastion onward isn't a midpoint.
It's the beginning of the endgame disguised as a midpoint due to the second visits.