I don't see the big deal, TMNT have had their source material changed constantly from day one with most aspects of it. Most people grew up on a source modified from the original concept anyways. I'm most familiar with the original animated series, like most kids from the 80s, but I still enjoy almost all incarnations of it.
Do wish they'd give Casey Jones bigger roles though, like the first movie. Hell they could probably make a full feature film from him alone.