Judge it for its time...
A lot of first-time viewers seem to watch this today and view it as a piece of crap, HOWEVER you have to take yourself back to when and how it was made and to its time and place in movie-making which was SO very, very different to today.
I first saw this back in the 80s and have recently just revisted it and YES the production values are low and disjointed, but there's a definite sense of style, creepiness, gore-iness, fun and innovation about the whole thing that deserves full marks for effort and originality!