Kinda sad that Nintendo could have something so popular be followed up with a system that had backward compatibility and yet flop so hard.
I had a Wii U almost at launch and waited the whole time for a major "killer app" release that never really happened. Splatoon, maybe? In summer 2013, I thought Disney Infinity would help a little, but that was on every other console as well. Then I thought Zen Pinball 2 would do something for the system, but these were third-party titles.
There were quite a few games that were fun, like Super Mario Maker, but they weren't killer apps. Perhaps if Zelda: Breath of the Wild had been released sooner and made to use both displays (which I speculate it was made to do while in development), more people would have wanted a Wii U.