There are a lot of reasons why the Wii U didn't sell other than software, but also other than MK8 and Smash, I don't think there was a real system seller for the Wii U in those first two years. Mario was underwhelming, no Zelda title, no new ideas (until Splatoon which was too late by then), and underwhelming 3rd party support.
Obviously, this was all compounded by a weird name choice, bad marketing, and a confusing controller. But make no mistake, while there were a few gems, I consider the Wii U software lineup to be the worst out of any Nintendo mainline console game.







