The mighty would have fallen by now, but their reputation is propping them up. That’s how it goes when your rock band becomes too big to fail. You grab enough people by the heart when they’re young and impressionable, you get to be a big deal forever, whether your moment of excellence lasted well over a decade (like U2 or the Rolling Stones) or just for an album or two (like Weezer and the Strokes). Call it brand loyalty, wishful thinking, whatever. It’s a fact of the music business. Creative death can’t kill the world’s biggest rock bands — only actual death, and sometimes not even that.
I’ve only heard a couple songs on the new Arcade Fire album, so I can’t comment on that directly, but I do think this is an interesting phenomenon in general. When an artist’s prior work creates an unstoppable gravitational force of fandom.