I think the biggest mistake with the Wii U is the chipset.
People just don't want another PS3/360 machine. I'll grant you even the Wii U is a better hardware than both and an upgrade sure, but not enough of one, certainly not for a machine that's launching *seven* years after the XBox 360.
It needed to be something that absolutely destroys those systems no question and can run every PS3/360 game in 1080p at least.
By choosing to stick with the "we don't make graphics intensive consoles anymore" routine, what Nintendo unwittingly did IMO is actually make the system less unique. A large graphical upgrade + a new touchscreen controller together is probably enough "newness" to get more people to bite.
But another PS3/360 type console (ok, a bit better, but not enough for devs to care) + a relatively moderate "wow factor" controller was a poor recipe to begin with.