It started out very much as a parody of Star Trek, though some fans argue otherwise, and it was
reviewed as such when it started. MacFarlane desperately wanted to do a Star Trek show and couldn't do it officially. Parody is a protected form of speech whereas just ripping off something to the point of hiring writers, producers, and cast members from real Star Trek could get you sued. So, hey, yeah, everybody, it's a parody. Then he gradually made it more serious, but that didn't really work for me either, though by then evidently it was clear he wouldn't get sued.