Enterprise is almost non canonical in that they took too many liberties with the timeline. Berman stated that it technically wasn't a Star Trek show, but just "based on" Star Trek. That's why the title is just Enterprise and not Star Trek: Enterprise. It was supposed to be a departure from the norm, but ended up just being a mediocre show. I think Berman just said that mainly because it freed him to mostly overlook the previously established timelines and "sexify" the show with the half nude shots of T'Pol in the decon chamber.
