From an art perspective I thought TWilight princes was brilliant, I don't really know what else you can ask for. It some amazing designs for the twilight creatures and such, I loved it. I'm guessing it was too close to early games in the series for him. Maybe he was hoping for Zelda to attain to some new artistic level. Wind Waker certainly pushed the franchise in a new direction I guess he wanted to see Twilight Princess do the same.