>>9935358
The very different types of obstacles and challenges (not to mention locales and even mechanics) in each Zone tend to cushion the arguable negatives of lacking a strict overarching difficulty curve, and there still were encapsulated difficulty curves inside each "set" of levels. That's a more than acceptable general template to design a game, as the Mega Man series proved; whether it fits a Mario game is again arguable, but it'd be weird to argue it as particularly jarring or inappropriate.
Also, in GB games it was an understandable trend to offer a choice of variety out of the gate because portable systems would often involve shorter casual play sessions when actually used in a "portable" context like a commute for example. Devs who didn't think of that early on quickly realized it made sense, like Konami with the second GB Castlevania for example. Granted, this factor may have been redundant in this case given SML2 saved your progress lol
Anyway, I think the game is fine and it's fever-dream tier creative in general compared to its predecessor and Mario games in general. Though I do dislike the stiffness of the controls in comparison to the first, and also the Wario games are definitely more fun and unique.