The game is as lenient as it gets, it is a guided tour throughout the safest theme park ever, it takes you by the hand and sings you a lullaby in case you feel scared of a bush, there's virtually no challenge that can't be overcome by stopping for a second and calculating the next jump, and I'm not talking Castlevania NES level here.
The game makes sure from moment zero that you're aware of the situation at all times, safe, in a fenced cage, a colorful, simplistic and dystopian purgatory of easy platforms, shoving things in your face with no text, in case you don't wanna read about the blandest story yet in a Mario game.
If you die a few times, a white tanooki suit is handed to you so you can blitz through the level being invulnerable, what's next for Mario? tutorials on how to get coins by breaking blocks? Don't even get me started about the stars and collectibles...I have not felt so insulted since the ridiculously easy "puzzles" in Uncharted
You want to know what I consider a proper platformer? : Rayman Origins/Legends is leaps and bounds over NSMBU and SM3DW.
Oh and BTW, NSMBU is a 2 dimensional game, it doesn't have "one dimension", unless of course you're referring to how soulless it is in a poetic way.
This is why modern Nintendo games are so overrated.