That likely didn't leave them much time for detailed new concepts and refined inspiration. I imagine the design meeting for Super Mario 3D World involved one man standing up and screaming "Mario 2!", another man screaming "In 3D with multiplayer!" and the third man bellowing "AND WITH CATS!" and then they made the game. It's the videogame equivalent of putting a semi-naked attractive person on a pile of money-covered pizza. It's base and it's crude. Some might even call it slutty. But it works.
Mario 2 in 3D with multiplayer and with cats didn't blow my mind with it's ingenuity or innovative gameplay mechanics, but it made me pretty darn happy, and that's more than enough.