I don't mind its target audience, or even its design. I hate it because it pisses all over the personality of the original characters, and makes them look like selfish, annoying, stupid douchebags. Example? Raven: she had always been dark and distant in the original show, but not to the point where she literally, and happily, dreams about killing all her best friends. Also, it was also true that, in the original show, Raven always found BB annoying, and seemed to dislike him, but not to the point where you could never tell that she secretly had feelings for him as a friend, whereas in TTG, Raven has no problems telling BB how much she hates him and will never have feelings for him.
I hate TTG because it turns the characters who I've loved and have been watching for years, and turns them into assholes. BB is brain dead and selfish, Cyborg is oblivious and annoying as hell, Robin is self-centered and idiotic, Starfire is nothing but Robin's ditzy love interest, and Raven is bland and unlikeable. It butchers their personalities.