It depends on your perspective really, but from my eyes Nintendo decided 'oh lets make this giant controller to fight the tablets' instead of actually fighting the other home consoles by making the Wii U's specs competitive for next gen, instead they seem more matched to competition with the 360 and the PS3. Therefore you could argue the lack of 3rd party support is justified as developers don't want to waste time on less powerful console. Their game will also be probably be less successful on Wii U due to the larger casual audience.
By putting the Wii U out there so early they basically have restricted themselves to using Mario alone to sell consoles. I suppose for many on here the Wii U is their perfect console, but for a wide amount of the gaming audience it's pretty poor.