I bet the fact that Casey Jones wears a mask is the reason why we can't have him in this film. Any larger-than-life characters from the source material have only left out as the secondary need of the journey: the turtles are now plot devices and the Shredder is, for some reason, a henchman. Instead of fearing the Foot Clan, the threat would rather focus in some evil corporal manager. Instead of being about the Ninja Turtles, it rather centers on April O'Neil. It is clear that if follows the same screen writing rules of the last Bay franchise. The film does have some rewarding moments, but it just keeps hindering us to the less interesting parts which makes it disappointing. Which is a shame, because it somewhat gets it right with the turtles, their stories are more interesting than the one we ended up seeing.
The real sin of these movies is its lack of interest to its main heroes and instead focuses on the human characters. At the post-viewing, maybe we can accept the heavy reliance to cartoony CGI, or the large amount of explosions, or the really poor plot. As the same as the public response about the Transformers franchise, people turned out to be ranting at the wrong stuff. But as a producer, does it affect much to Teenage Mutant Ninja Turtles? Surprisingly yes. No matter how the name Michael Bay is attached to a fantasy adaptation, people will complain anything about the project.