You're probably right overall--though they didn't "quit" right after becoming "superstars," which would have been what, 1991? They lost their drummer, then signed a jillion-dollar contract that didn't really pay off for their label, then awkwardly returned to cult status, as Erlewine put it. And now they're 60 and Michael Stipe has a hideous homeless-guy beard.
Maybe "End Of The World," "Shiny Happy People," etc. will keep being used in movies, but that's their best bet for "staying in the cultural conversation."