While the points being made in this thread are valid, I would argue that even if the Wii U concept had been better executed (featuring stronger first party games, robust third party support, a lower price, more powerful hardware, and a longer six year lifecycle) the console potential would have still been capped at maximum 40 million units

Wii U's main problem was Nintendo

Nintendo's reputation in the home console market at the time was kinda shaky. Many consumers viewed the brand as unreliable for delivering long term support for stationary consoles. This perception was a holdover from the Wii era, which, despite its commercial success, left traditional gaming audiences feeling alienated due to its casual focus and underpowered hardware. Worths nothing Wii followed the atrocious Game Cube and the very divisive Nintendo 64, at this point we had a whole generation of gamers who had never seen Nintendo systems as an option to a main console  

Compounding this was just a lack of trust among gamers who wanted a dedicated home console experience

Imo, Nintendo took to long to embrace HD development. The general perception was Nintendo was a very poor HD gaming developer (and by some extent I agree with that feeling). This issue reinforced the broader notion that Nintendo excelled in handheld markets but lagged behind in the home console space, pushing people further away from Wii U

The 3DS, for example, often received the same franchises as the Wii U such as 2D Mario and Smash Bros at a far more affordable price point. This undercut the Wii U's value proposition, making it harder for consumers to justify purchasing the system. Remember: At this time Nintendo hardware was mostly seen as secondary console, PS4 was 400 USD and much more powerful, with better games and very goodwill from customers, if you are really dying to play Zelda or Mario Kart it's better to get a 3DS for 170 USD instead of a Wii U for 300 and the bonus is you get a console to play on the go

I Think the concept of a secondary screen was done better back with the Gamecube and GBA, at least in the game that took the best advantage of it.

The gamepad was more comfortable than It had any right to be, but I only used it for creating levels in Mario Maker. For all other games i played I used a pro-controller instead.
I feel like the gimmick did not fly and without that unique lure what is left is a less powerful unit than the competition at a price that was about a gamepad to high.

Agreed.

A good way to think about this is to reverse the question and ask what would have made the WiiU a success:

1. Would have needed a big critically acclaimed launch game that got people dying to buy the system: Nintendo always needs to launch with either 3D Mario or 3D Zelda, and potentially an additional casual game that set consumers ablaze with word of mouth like Wii Sports did.

2. Cheaper price, should have been $250/$300 not $300/$350. Wii was $250, WiiU was $350 for the one with halfway decent storage. Consumers expect Nintendo systems to be affordable so suddenly jumping up the price by 40% was an awful move.

3. Keep the hits coming. A must-own launch Zelda/Mario and optionally also a Wii Sports-like hit would have put it off to a great start but then you still need more hits coming soon after. WiiU didn't have that.

4. A completely different design. This is the main thing of course. Even with a cheaper price, a must-own launch game or two, and regular releases of great Nintendo games, it was still a horrible design that nobody asked for. As Curl said, Wii made gaming accessible and fun and social for gamers and non-gamers alike, while WiiU's design did pretty much the exact opposite. All of a sudden instead of a super simple fun multiplayer experience like the Wii created, you have an awkward one-player focused system with the other people seeming like secondary players. That sort of asynchronous multiplayer gameplay can be interesting for very specific games! But not for the basis of an entire system! Forcing the entire system to mold games to something that would only work for a small handful of game types was just a monumental blunder by Nintendo.

When they announced the WiiU my reaction was something along the lines of:

"that's kind of cool you can take the gamepad away from the TV and keep playing your game, could be useful in some family households, but that's not a system selling feature and for probably most people including myself is of very little interest, and wtf is up with only one giant expensive controller and everyone else in multiplayer games awkwardly not getting to play with the system's controller and having to use last-gen controllers??!"

So basically, no matter what you change with the WiiU's pricing/launch/software, the only thing that would have made it a success is if it wasn't a WiiU!

You can tell what they were trying to do with the WiiU - a halfway effort to what they actually made with the Switch. But it's like they decided on this strategy, and once they decided on it they never once questioned if it was actually a good design and if people would actually want to play it. Not to mention the fact that by the time the WiiU came out the excitement over the Wii had completely died as sales at the 3-4 year mark went from on fire to plummeting. So they brought out a very poorly designed system that was supposed to leverage the Wii to continue the Wii's momentum, but it launched like 2-3 years after all the momentum had faded from the Wii.

It seems like they didn't bother to do any market research about their idea, cuz you gotta figure if they did they would have heard a lot of statements similar to my own initial thoughts I mentioned above.

As always, so much attention is paid to the X's and O's of the situation, which makes sense. When something goes wrong, it's only natural to try to focus on that sort of thing. But over the course of the past few decades, I've noticed that in the console industry, it's really less about what you're offering, and more about getting people to think that what you're offering is what they want. Because think about it, how often does a console explode out of the gates because of some sort of objectively good decision? Are any of you old enough to remember the Wii, pre-launch? Everyone was laughing their asses off. None of us thought it would sell. All of us thought it was close to, if not the dumbest idea in the history of the industry... and then look what happened. Same could be said for the Switch. No, it wasn't quite as severe, but most of us were like, well, there goes Nintendo. lol

The reason the Wii-U failed was more about people at that time just being convinced that the other options were better. Whether that's marketing, some sort of bad luck, timing, or whatever... who knows. But the games on that system were great, and the sales of the Switch ports prove it. It just failed because people weren't convinced it was the right console to own.

So true. The GamePad was one of the aspects that sank the Wii U.

It added a lot of the cost to the console (about $79 in production costs which means over $100 to the pricing of the console at launch), was only usable by one player on the console, was required for some games, and even was required for the initial setup and tweaking settings on the console. Not to mention it had a resistive touchscreen, 480p resolution, and looks like a Fisher Price toy. 

Sure, a Wii Remote is required to navigate the Wii. But a ton of them were made and they're much cheaper than the GamePad. 

Nintendo really should've patched out the GamePad from being required for system settings and sold SKUs of Wii U without it. And of course, there should have been at least 2 Game Pad multiplayer supported like originally planned. 

First and foremost the problem was the games. There wasn't really any killer apps at launch. Although it had NSMBU, but it was very weak 2D-Mario. The controller made the system too expensive: when it didn't sell, the system should've been sold at around 150€ pricepoint, roughly half of what it was sold at.
The controller was used as a gimmick in most of the games; it worked with the minigame compilations and party games and games where it was used as a map screen, but the games that required your view to switch between the two screens really killed everything good with it. You also could use Wii Remotes to play games, but only multiplayer and you could not choose your controller. Remember how some Wii games let you choose between GC controller and Wii Remote and Nunchuck? Not on Wii U. The best use for Wii U gamepad was to use it as a second screen on Virtual Console and Wii games.
The best thing about Gamepad was it's D-pad.

Problem with the Wii U was the selling point being the gamepad wasn't a must-have gimmick like the Wii & Switch.

The Wii was a must have cause it made it seem like you can have a bowling alley or other sports in your living room using motion controls which were very simple to understand, it truly changed the game and was a gimmick never seen before and it set itself apart from its competitors enough by providing a gaming experience you can't get anywhere else.

The Switch set itself apart by allowing you to have the option to play console like games on the TV and on the go, it's been done before by other companies but it was far less seemless, and doesn't offer the games anywhere close to what the Switch offers. Many brought the Switch for the idea that they're getting essentially 2 consoles in 1 which stood out heavily against its competitors cause of its ability to play console games on the go in a way that fits many people's lifestyle

The Wii U failed to stand out much. The gamepad wasn't a must have feature. The gamepad did some cool things, but none of them made it a must have. For example, playing an adventure game where you'd need a map or inventory often like Zelda with the map & inventory on the Wii U gamepad right there to check without pausing out the main game was cool, but players could easily live without it, only makes checking a map like 2 seconds quicker which isn't worthy enough to spend 300$ on.

Asymmetrical gaming was cool, and for me personally I still really love the Wii U for that feature and made certain games only possible on the Wii U, but again it's not a crazy must have feature since not many games in the first place would use or benefit much from asymmetrical gaming.

Playing off the TV was also cool about the 2nd screen, but it's range was so pathetic to the point where it almost defeats the whole purpose of having it. You couldn't even go to another room with the gamepad without disconnecting from the Wii U, which made that feature only useful when someone else wants to watch TV, but very few times would a scenario like that ever happen. Again, it wasn't at all a must have feature.

All the Wii U gamepad did was add several cool nice conveniences, but nothing game-changing enough to wow people into spending 300+$ on it. A lot of the things the Wii U gamepad did people could live without easily.

With the Wii U gamepad not offering much innovation, what you had left was just an standard Wii that people already had in their living rooms for years and lost interest in the motion controls it offered for an expensive price.

The gamepad was a mistake, but had that been the only thing wrong with the system then developers would probably have just mirrored the TV's output to the gamepad screen and called it a day. Likewise, the whole kerfuffle about the console's name was something Nintendo had been through before with the 3DS; they'd turned it around there, and they could probably have done so with the Wii U.

No, the thing that really doomed the system was the hardware choices. I can't remember any other console from a major manufacturer where the hardware design was just so inexcusably bad on every conceivable level. The GameCube proved that developers would port to a Nintendo platform in cases where it was quick and easy to do so (at least until the storage space of its mini-DVDs became a limitation), but the fact that games originally developed for the 360 and PS3 often turned out worse on the Wii U was frankly a total joke.

double from technical problems

The problem ultimately boils down to Nintendo trying to reinvent the wheel again for no good reason and doing innovation just for innovation's sake without a real plan or idea for how that would work. Nearly all of the problems with the Wii U ultimately stem from that. The gamepad being a terrible gimmick, the price being inflated while the system was underpowered for said price and for a Nintendo product, and Nintendo having no idea how to market the system. Nintendo could have easily outsold the XBox 1 with a well-designed and marketed Wii 2 instead of the Wii U.