Ehh, I think it's more the lack of stuff for mainstream players to do. At the end of the day, regardless of how iterative and uninspired Call of Duty might be, it sells. Nintendo doesn't offer online play, or a shooter-friendly controller. They make good games, but their platform delivery (hardware and networking) is terrible, so the big-ticket games get ignored on those platforms. The majority of the market buys those third-party games, and since they aren't on the Wii U, the Wii U gets left behind.
I could find plenty of things to play from the Nintendo library. However, I consider the Wii U a waste of time for me because there is no Pokemon, no Fire Emblem, no online play, no sports games, and no "serious games," like Forza, Call of Duty, Halo, and no Borderlands. The games that interest me are basically just the platformers (as Nintendo's the only company who makes platformers I actually like), then maybe Mario Party and a couple of others.
The holes made by not going Nintendo are much smaller than the ones that'd come from going WITH Nintendo, so I don't buy their consoles. I don't care for playing several games at once, so having multiple consoles does me no good.