These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
So Okay, It's Average: Some people defend it as a decent fighter (especially good for a licensed game) while others attack the small roster and lack of major TMNT fanservice, but the general consensus is that it's this. Disappointing, considering it was made by one of the same devs who made the critically praised Brawl.
The Problem with Licensed Games: People who have played the game claim it's actually quite good, but some reviewers compare it to Smash too much, rather than think of it as its own separate game.
One common problem it shares with this trope: there is very little content. A story mode that lasts a whole 30 minutes, a repetitive survival mode, and 51 extremely short honestly-not-stolen-from-Super-Smash-Brothers-Missions. That's it.
Villain Decay: The Shredder, in the Comic, he leaves the Fugitoid as bait for the Turtles, while having the parts nearby.
They Just Didn't Care: Many fans feel the devs simply didn't care about the game; despite being released to mark the 25th Anniversary of the series, the game only has 13 characters from the series... and then 3 characters from Ubisoft's own franchises. The 1980's series (you know; the single most famous thing about the turtles) is not even represented aside from a commercial in the special features and the Technodrome being the background of a level (the level you can't unlock without using a cheat code).
It's not hard to find lists online from angry fans of valid TMNT characters that were left out of the roster in favor of Rabbids. One such list on a Ubisoft forum had 150.
Oh yeah; don't forget that one of the characters and one of the levels are physically impossible to unlock without cheating.