I can't speak for Carly Rae, but fun. is definitely one of the best live acts in music today. There are few pop tenors as natural and consistently spectacular as Nate Ruess, not to mention the considerable musical talents of Andrew and Jack, who are no slouches. You can say you don't like them, but there is no universe in which they would be considered "shitty."
I also came in here to say I love this song and am thrilled that fun. is covering it.