The central reason smart people (and certainly most critics) disparage nostalgia is utilitarian: It’s an uncritical form of artistic appreciation. If you unconditionally love something from your past, it might just mean you love that period of your own life. In other words, you’re not really hearing “You Oughta Know.” What you’re hearing is a song that reminds you of a time when you were happy, and you’ve conflated that positive memory with any music vaguely connected to the recollection. You can’t separate the merit of a song from the time you originally experienced it.