That's just what you want and not what should be necessarily in the game. Original worlds need to be the lenght they're supposed to be to fulfill their purpose.Should have delayed the game a year or two to make the original worlds, actual worlds.
Spoiler ShowTwilight Town: It's disappointing because it's smaller. It's the hub world, so no reason to not at least fully recreate
Keyblade Graveyard: It's a wasteland, how can you make it interesting? It's a battlefield and this is its purpose
Realm of darkness: Aside from the fact that we have already explored it in two games, its purpose seems to be "Get in, Save Aqua, get out", so it's totally fine if it's just 2-3 areas (and this is KH3, the areas could be big enough)
Radiant Garden: Major disappointment
Scala Ad Caelum: We don't know much. The leaker went from "not explorable" to "it is to some extent" to "and inch and you fight the final boss"
You can and should be disappointed about TT and RG, but Nomura owes us nothing on the rest. So no, not even a 10 years-delay would have been helpful if these worlds were meant to be like this all along.