editing can do a lot for a film. Supposedly a test screening (opening?) of 2001 went over poorly (although even today there are widely mixes reactions) and Kubrick went out to Sam Goody or something and bought some classical music to rescore the film.
One of the great missed opportunities in SciFi cinema was when the powers that be, seeing the success of Star Wars, approved a Star Trek movie and the creator decided that his inspiration would be the spectacle but plodding boring pace of 2001 instead of the exciting space opera of Star Wars. That movie is all but unwatchable because of that dumb choice and a proper Star Trek movie at that time, right on the heels of Star Wars, could have been massive.