Bad sales or not, the console still has a lot of good games that can be enjoyed
The console was just horrendously marketed. I think that there are a lot of people out there that hate the Wii U either because they don't think the console has good games, or that they simply hate it for the sake of hating.
No, Nintendo lost there way since GameCube, they got very lucky with Wii since it was a huge fad due to its moco ability, but since Wii they've been making consoles that are incapable of running most of third party developer's AAA titles. This is what's truly wrong with Wii U.
Since Wii, Nintendo has made consoles, significantly weaker than their competition, thus incapable of running any third party developers biggest sellers on par, so what happens is true core gamers end up getting the competition consoles, and third party devs unable to make their AAA games run properly due to hardware limitations start to abandon the Nintendo console. It becomes a vicious cycle, where more and third party devs start to drop support for Nintendo in favor of XB1 and PS4 both capable of running more of less the same caliber of games. With fewer and fewer third part devs supporting Nintendo's inferior hardware, more and more core gamers start to drop Nintendo's console and move onto MS and Sony branded hardware.
If you look at Nintendo's heydays, they were always on par with their competition in terms of sheer hardware capability and always enjoyed descent if not stellar third party support. No console can survive without third party support, hence releasing hardware parity with your competition is vital to being able to maintain a sustainable business. Nintendo dropped the ball with Wii, they started to believe in their own myth, they actually believed that releasing hardware that was one generation behind its competition was a viable business move, and Wii U showed them that they were wrong. As a third party dev, you will not go out of your way to nerf your biggest AAA title to run on inferior hardware, you will just pass on that hardware to develop on hardware that will run your biggest titles. This what Nintendo did not fully understand until it was too late.
But it sounds like Nintendo intends to rectify this with NX, who knows.