Here's what I think happened: Nintendo was planning on leaving a lot of room for third parties to take the spotlight on the Wii U, as they often complain that Nintendo gobble up all the game sales on their own consoles. Then third parties looked at the Wii U install base and said "nope," so Nintendo had to act fast to try to pick up the slack.
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.
[*].disqus.comto your security software's whitelist.