It's not so much awful as it had potential and it wasn't fulfilled. Some of the problems came directly from pandering to the film's detractors, like making Oroku Saki Shredder yet keeping Eric Sacks in the film, giving him partially Shredder's and Baxter Stockman's scenes, pushing both of them to the side. Stockman was completely cut out of the movie. Shredder felt placed in.
Add to April being the center of the action and not portrayed by a very good actress, I was actually a little disappointed it wasn't as loud and blowy uppy as a Transformers movie. Could've actually helped. Not that there wasn't some actual good in the film. The turtles were actually quite good! Just not enough of them. But it's hardly the worst thing associated with the Turtles. I'm just hoping they learn their mistakes in time for the second movie. Have it focus on the Turtles, Splinter, and Shredder this time. And if you have to focus on a human, please make it Casey Jones. And don't make this the film to forgive Shea LeBeouf and cast Casey right.