I think that it's a combination of issues that are killing the WiiU - but honestly I think very little is Nintendo. Here's why:
1) As many people have said, the PPC proc is outdated. Like ooooooold, no one uses that anymore. This doesn't mean weak; it's just out of 'style', shall we say. And, hard(er) to develop for. Why would dev's spend time and money porting code, optimizing, and creating _system specific_ features while they could just port their code, 1:1 to a PS4 / Xbone and make the same amount of money?
http://www.craveonline.com/gaming/a...-2-months-to-get-a-aaa-pc-game-running-on-ps4 vs God knows how long for a PPC port *cough* Watch Dogs *cough*.
2) The titles on the WiiU fail to inspire. I haven't even beaten NSMBU but the Wii one? Tons of fun! I'd pick the Wii version over U any day. Super Mario 3D World? Alright. Had more fun and 100% SM3DL. Smash Bros. Brawl? People were going crazy, and it was a HUGELY anticipated game. SSBU? I've checked the site, maybe twice? I find myself using my Wii much more than the U.
On the other hand, I'm debating picking up a PS4 for Second Son, and honestly Titanfall / Forza is enough to sell me on an Xbone. [Disclaimer: I don't play online, so PSN / XBL I could care less].
There's no must-haves for WiiU. While that could change...I feel it's unlikely. Might just be us gamers getting old, but I don't even see Kids asking for WiiU's.
3)
This is the one I think is not discussed enough: Apple. Why apple?
Well, the WiiU is conceptually similar to the DS. It's been stated by Nintendo that the Wii was even based on the DS, then scrapped (I suppose this recycled idea became the WiiU?
http://ca.ign.com/articles/2012/12/07/wii-u-was-once-a-wii-zapper-prototype, I suppose not, but I'm sure elements of this played into it).
This was pre-2006. We were all using Blackberries and Palms and touch was the in thing. I'm sure Nintendo thought that a 7" touch screen / second screen would be revolutionary, and indeed, it would be.
But what do we call the WiiU? A tablet. Why? Because Apple. Secretive as they are, they catch the world off guard with their iPhone and then with their iPad. Google also releases Android which breeds tablets. This is 2007-2010. Fast forward to 2012. Everyone and their Dog has a tablet. Which, by the way, cost a lot of money. Suddenly, Nintendo's revolutionary isn't, anymore. It's out of date:
before it even launches. The entire concept of a second screen, which could easily be achieved with an app or something, is suddenly old news. Nintendo launches, consumers don't want another tablet that, as mentioned before, can only be used in their house, and the rest is history.
Now, this is where I agree with some people. Nintendo's hard-headedness somehow made them think a 7"
resistive touch screen could somehow compete with their own console, which had the same name, and tablets, which people had. Most consumers aren't gonna buy it, especially considering the marketing is non-existent to distinguish it and set it apart. So why buy it? Games, 3rd Party Dev's aren't gonna fix the WiiU. Nintendo's willingness to adapt? That's what's keeping it back.