Part of nostalgia is nostalgia, but part is hearing loss. It's harder to appreciate new music when we can't hear the higher frequencies any more. We remember what the songs of our youth sounded like, including the higher frequencies, and our minds fill the missing parts in for us.
It’s more than that: If you’ve not done so already, check out “the loudness wars” (over-compression of the dynamics). It’s bad enough to know or remember what it should sound like (and maybe one’s brain can fill in, but MINE tells me what’s missing in the re-playing itself!)....
New music with no life left in it is even worse.(!!)