Alternative perspective:
The Wii U was a failure because of an utter and complete failure at marketing, of the same kind that doomed the Dreamcast back in the day.
* The name is awful, and led to frequent confusion about it being an addon to the Wii.
* It got almost no advertising, especially when compared to the Wii, and especially the Switch (which got a freakin' super bowl ad!)
And then the more technical concerns:
* Poor support all around. A number of first party franchises like Metroid never even had a mainline game on the system, and we know the third parties were absent.
* Dual-screen concept doesn't map well to a TV. Star Fox Zero is a crying shame because of this. The game is a pain in the ass because of the switching between screens, and it could be so much better without it.
* Expensive: $350 at launch.
Contrary to popular belief, I don't think the console's under-powered-ness was the big problem. Nintendo's been developing consoles that are hardly cutting edge for well over a decade now. I think the problem was the marketing failures and the low attach rates convinced the third parties to not even bother.