The problem is that this was billed as a celebration of Ninja Turtles history. People feel like they haven't seen that celebration, with all their favorite characters, and now instead they are getting an advertisement for other Ubisoft games. That's a raw deal, and don't pretend it isn't.
If you took out all the characters and replaced them with sock puppets, you could theoretically have the same "gameplay." But no one cares about the gameplay if there isn't a great context for that gameplay. Suddenly the context of "a celebration of Ninja Turtles history" is being pissed on.
An appropriate "cameo" or "easter egg" would be a single, unlockable Rabbid, dressed as a Ninja turtle. Then it would still be in the spirit of "a celebration of Ninja Turtles history." Instead there are two different versions of Rabbids announced before TMNT characters that people in this thread are calling shoo-ins.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
