I don't blame them, it's a business decision and one that seems correct. I played Zombie U, it was fantastic, it sold so poorly. I played their other ports of AC III and AC IV and thought they did excellent jobs.
What more can they do? In fact, out of all the major 3rd party studios, they put the most games on the system.
I look at other forums, not based on gaming and the general view from casual's of the Wii U is it's a weak console for babies.
Now, I know that's the wrong opinion, but that's its perception. Most people who bought the system are die hard Nintendo fans with interest only in their first party games like Mario and Zelda. Of all the people I know who have one that seems the case.