tbh King Crimson themselves were quite a bit different from others of their time. Dream Theater & co. probably took more from Yes, Camel, and ELP than King Crimson, Gentle Giant, and the other more experimental bands. So yeah, most progressive metal is far from "progressive" in the literal meaning of the word, and a lot of it doesn't even fit in the sense that it's supposed to be technically challenging, but the number of truly progressive bands has always been miniscule. There were hundreds of uninspired prog rock bands of the 70s as well (see: Starcastle).