Prog is among the more divisive subgenres of rock music. You either love it or hate it.
That said, it's kind of fun to look at that post-punk period, around 1979-83, where prog bands either radically transformed their sounds and went MTV mainstream (Yes, Rush, Asia, Genesis, Styx, Journey, etc.) or suffered through creative struggles and personal hardships before disbanding or fading away (Kansas, Gentle Giant, Camel, others).
King Crimson, who went through its third major lineup change when Adrian Belew and Tony Levin joined up and Bill Bruford returned to the Robert Fripp fold right before Discipline was recorded, ended up occupying neither of those spaces. It became even more of its own thing.
Here's some great footage from 1981 and a great review of the Discipline re-issue (the album originally came out in September of 1981) on All About Jazz.