It's about the Games not how Powerful the System
That way of thinking died with the Wii and PS2 basically. With home consoles now its about the most powerful hardware gets the most/best games. Many major developers don't want to work with the Wii U's weaker tri core PowerPC cpu and smaller hard drive size, so what you are getting for the system now is Nintendo exclusives and HD remakes, and a lot of kids games and digital download titles. You honestly cant blame them. Current mainstream games are just becoming more and more complex, and they eating up more and more hard drive size as time goes on.
Developers now want quad core and above fast cpus with out-of-order execution, a solid gpu, lots of ram, and a large hard drive. They want to make games on platforms that are easy to port back and forth to between the consoles and PC. They were very verbal about this and Nintendo chose to ignore it all in favor of cutting cost so they could get the tablet gamepad worked into the total price.
Because Nintendo wanted to ignore everyone, current ports the Wii U gets even struggle some to keep up with the 360 versions performance, etc. It is only going to get worse and worse as development for the 360 and PS3 slows down, the PS4 and Xbox One ramps up, and the Wii U gets expected to keep up with the later two systems and perform on the same level (which it cant).
And you also have the casual players and older generation that Nintendo captured during the Wii's time at retail that have been lost due to the Wii U's cost, under-performance, and the tablet controller adding complications to gameplay that casual players, small kids, and older people don't want to have to deal with. Even though Nintendo is unhappy about it, the fact of the matter is that the Wii U has become a niche product whose customers will mainly be Nintendo diehards or gamers with money to burn who buy more then one console, and it's Nintendo's fault it happened that way.
Maybe they will take this as a learning experience and bring something more compelling to market next time. It's an expensive lesson to learn, but Nintendo had to learn it sometime.
Anyway, the good news is you Wii U owners do get Mario Kart 8 this month. The bad news? You don't get Watchdogs and Wolfenstein: The New Order. Hopefully you kept those 360 and Ps3 systems on hand at least. Blazkowicz is depending on you.