The Wii U was a massive failure, precisely because of a lack of third party titles. Nintendo has great ip, but they don't push out enough games. No real Metroid in quite some time and Mario won't even hit the switch until end of year. Other console manufacturers have been far more successful than Nintendo recently.
Edit: to clarify, I love Nintendo, have since the 80's. It's not true that they've been killing it for decades though, Sony has been eating their lunch off and on since the PSX.
The Wii U was essentially a failure because Nintendo thought there was still a market for a chained-to-a-TV console—and there is, but only in the "hardcore gamer" segment that don't care for Nintendo's games lineup. The segment who are interested in Nintendo games, have shifted to being far more interested in mobile games than TV-console games (even if they would enjoy playing those games on a TV once in a while.) The Switch is an acknowledgement of this, and that's why it's succeeding.
I don't follow gaming news closely, so when I heard of the Wii U I thought it was a hardware revision not unlike the Xbox One S to the Xbox One. It took me over a year after launch to learn that the Wii U is an entirely new console.
The same thing happened with the 3DS. When I finally looked into getting one this past holiday season, I was confused by the 3DS vs 3DS XL vs New 3DS vs New 3DS XL. I was hesitant to buy since I wasn't sure if the New 3DS was a hardware revision or an entirely new console like the Wii U.
On top of that, the marketing wasn't there for me. I learn of my gaming news when it hits the front page of Reddit. When the Switch was announced, there was massive hype behind it. I didn't see the same for the Wii U.
You know, people level the same complaint at the iPhone, but it doesn't seem to have caused Apple any difficulty selling them. Maybe it's just that Best Buy/Toys-R-Us/EB Games employees aren't as good at helping people find the right model as Apple Store employees are?
On the other hand, the iPad's numbering was eliminated on its 'primary' model around the time of what would have been the iPad 3. That, in conjunction with the four different sizing options, seems moderately confusing and not consumer friendly. Not sure that that's why the tablet market is declining, but it might be contributing.
It took me until about a month ago! I skipped the Wii and never considered the WiiU because I thought it was a Wii expansion, and as such I figured I'd update when the next console was launched (Switch). Once it was, I did my research and realized that the WiiU would've been a fine purchase for my purposes (retro gaming + nintendo first-party games for WiiU and Wii).
If I'd known what I know now, I probably would have bought a WiiU a few years ago.
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.
They lost against the PSX as well though (iirc, 3x more PS1's sold an far more games.) They struck gold with the Wii initially, but at the same time, moved further away from the mainstream gaming crowd. Many games were little more than poorly implemented gimicks.
I'm hoping they hit a home run with the switch, but it's too early to tell. I have one and, while BotW is great, I have nothing else to play.
I've tried to get into gaming lately but the console stuff is just so contrived and dull. It's so focused on trying to be a movie (a bad one at that) that it has completely killed any idea of fun. The COD series is the absolute worst culprit. I really don't want to sit through a cutscene, then spend 30 minutes figuring out how the game works. I just want to play.
But Mario, Zelda...they're all just pure FUN. This is gaming as I remember when I was a child.