I have to say I agree some but over all I think you are judging the game too harshly. As someone pointed out a timing based platformer isn't even out so to hold it against NSMBU that it is something that doesn't exist seems a bit silly and fits into your own post about what bias really is. How is requiring Nintendo to do something nobody else has not an unfair preference?
I don't see how the game is as uninspiring as you claim but it is the first one I played in 25 years probably.
"The co-op is a lot of fun with 2-5 players playing at once on the same screen. " wait what? No you cant play 5 players on screen at once. Whoever uses the game pad is helping the others by tapping on hidden blocks or creating platforms for players..okay you did cover that after that but that part seemed odd at first because 5 player isnt on screen.
How many Mario games are on Wii U? Does that mean you will count off on games in their 5th or 6th run in a single generation if 1 game per console is flooding market?
I don't disagree with your score really. Its just your reasoning behind why you scored it that way just dont seem valid.
I have Mario on now beside me. I hardly call it easy. Sure I beat the game a while back but that is not the same as finishing it. I wont be finished til I have 100% but since you think jumping Goombas til you get 40 one ups is easy you must have completed everything in the game fairly quickly? Or did you skip 7 5% of the game like a casual player would? Does that mean your review is from the casual perspective since you took that approach to the game or did you really 100% so easily?