Honestly, IMO, people weren't as good at this kind of movie back then, and audiences were less informed as to genre elements. The weirding way, the Voice, even

Honestly, IMO, people weren't as good at this kind of movie back then, and audiences were less informed as to genre elements. The weirding way, the Voice, even the psychedelic sequences - these had to be explained, or shown, and how? How do you film these things in a way that audiences can understand? Not saying there's clear answers now, but there's been another thirty years of exploration in how you show weird, hard-to-film genre elements. There's also another entire set of explorations on exactly these things (the Scifi Channel's miniseries) from which to see what works and doesn't.