I assume you have an issue with Raph taking all the bells of the mannequin in the smoke without a sound in TMNT2 as well? Honest question.
tmnt is no more realistic when it comes to this particular issue than the fellowship of the ring. Skilled characters can sneak around with back backs on. It's fantasy.
Actually the bell thing is a good example of ninjutsu, actual ninjutsu. In modern media, TMNT as well, ninjas are skilled super confrontational warriors, not resourceful in the art of nothingness. Shinobi were most concerned with never being spotted, heard, or identified. The bell scene, while largely "Hollywood" is something I can suspend disbelief for. Ditto for Don in glasses, a backpack, etc. Thing is, that he has SO MUCH on him that the design starts to stretch the limits of what I am going to believe in terms of concealment.
I get they wanted to present him as the tech guy, but it feels a bit much for anyone to practically use all of that equipment, even in fantasy let alone hide in the shadows with a giant mobile command center of sorts. It's not bad if this is what he wears some of the time, but if it is, as I suspect from the promotional material, throughout much of the movie; I don't know if I can dig it.
How can he even slide down the mountain in the humvee scene? Is the backpack greased up? Are the cameras going to break off? etc. It's just a lot in terms of mobility.
P.S. TMNT 2, is like... the perfect Ninja Turtles movie for me.