When it comes to new stages, Pokemon is the only one from the base game that feels egregiously absent - most of the other newcomers either got new stages (Inkling, the Belmonts) or had enough stages in their series that "fit" (Isabelle, Ridley). The fact we didn't get an Alola stage for Incineroar is still weird to me. Like, new Mario and Zelda stages, and a bunch of Gen VII tracks... but nope, nothing. Maybe the lack of HD assets for reference/conversion was an issue.
K. Rool is close behind. But that's more a symptom of "Donkey Kong stuff is all jungle themed" than anything else. There's a hundred cool locations across five DKC games... but I guess none of them are "iconic" enough.