Looks are always deceiving
Honestly, they just need to move past the whole NSMB 2.5D art style at this point, they've been using it for the past 15 years.
I agree, maybe a new 2D sprite-based game in the style of Sonic Mania would be nice. Also, have more playable characters like Peach, Daisy, Rosalina, and Pauline and not have Peach kidnapped. Peach being kidnapped in the NSMB series in NSMBWii and NSMBU is what made the series monotonous. If they are to make a new 2.5D game, make it be something other than NSMB and make sure it isn't about Peach being kidnapped.Honestly, they just need to move past the whole NSMB 2.5D art style at this point, they've been using it for the past 15 years.
Now, you're talking about the 2D Mario game that I've envisioned, a game that's Metroidvania-esque. It should be made.For me it would be interesting if there was some sort of 2D overworld based Mario game where all the areas are linked together, sort of like Super Mario 63 or Super Paper Mario except there isn’t even a resemblance of a hub world, just a giant 2D overworld.