I don't think the Wii U is an issue for the average gamer I think the price is the real stumbling point because many don't consider it 'next-gen' even though specs aren't the only thing that define that.
I think it's poor sales are a combination of the price for some but also atrocious marketing, I'm from the U.K and barely anyone knows it exists.
Nintendo are bringing out games so when people do pick it up there will be lots to choose from.