Where Nintendo succeeded with the Wii was taking the so called Blue Ocean Strategy, selling to non-gamers.
The problem is that the very people they aimed at last generation may not even know of the Wii U's existence, if they do see it in the stores there really isn't anything to hint that it's a new console.
Wii U makes it sound like it's just an updated version of the Wii, much like the 3DS XL is an update on the 3DS.
They would have been far better off giving it a different name that doesn't allude to the Wii at all.
It also looks too much like the original Wii, it looks like a Wii with rounded off edges, it would have been wiser to give it a completely different look, previously no Nintendo console resembled its predecessor.
To the casual observer the Wii U looks like a redesigned Wii packed in with a touch-screen controller.
To the more dedicated gamer it offers nothing in terms of power that the now previous generation offerings from Sony and Microsoft offer. As developers stop developing for the PS3 and the 360 the gulf in power between the Wii U, and the PS4 and XBox One will make it more difficult and less appealing for developers to develop for the Wii U. This leaves mostly first party games, which aren't released with any frequency and are often more of the same.