I really like the NES Mario games stronger combination of fairytale and urban aesthetics. You got Alice in Wonderland shrooms, chestnut people, fungi people, the evil ox dragon king's army travel the skies with their pirate airships, impossibly long vines that reach to a land of clouds... which come out of bricks, and you can travel to anywhere in the world... via its magical plumbing system! I know like warp pipes and brick blocks are still a thing but... that's it, I don't think the series had experimented with this approach enough in my opinion.
The franchise gradually became more self-referential, which is what happens when a series develops its own identity, but I feel that the fairytale elements died off because of that and I want to grieve over the lost mythological flavor first. Like in SMB3 you come across the Takarabune straight up, you can gain the powers of a tanuki and turn into a Jizo statue, these bits of the game share one thing in common, established Japanese myth. This is what I mourn the most, when pieces of mythos and history from the developers' cultural background weren't exclusively reserved for a specific segment of the game like Odyssey. Nintendo mixed the generic European fantasy tropes with what THEY knew even if it wasn't something EVERYONE around the globe could recognize and did so casually.
The special frosting of the original trilogy's worldbuilding cake that makes it especially original is the americana, because of course these games went with two Italian American plumber brothers as protags from Mario Bros for SUPER Mario Bros. So? Bricks, pipes, blocks, a sort of city construction theme but imbued with that unique mix of fantastical attributes. This was done with purpose, this was a deliberate decision to smooth the transition, this wasn't taken as granted. The floating city of New Donk exists but what it brought to the table weren't made a staple, y'know what I mean? This brings me back to what I said about Odyssey earlier, not only were the fairytales isolated but also the urban flavor.
I think as these games grew more popular, fairytales were replaced completely by contemporary cartooniness and the bits of working class American city life subdued. Dunno, I can't say I hate the Mario World after the not even so drastic shift, it built its own great style, but it'd be neat to see'em tinker with what originally made some of the series most famous iconography again, that old blend. I blame replaying All Stars + SMW for all these words.