Because, as you age, there's always a period in your life where you identify the most with the music, and most people tend to think everything after that just isn't the same. Most people, the cutoff happens when their life starts to shift focus away from music, but sometimes it's just that you identify with a specific period's music and anything else blows.
There's plenty of great music after 2000. In my opinion, the 90s had the LEAST good music, with probably the best music coming from the LATE 90s up through 2004 or 2005. I feel like the music before that (at least back to the 80s) mostly was kinda lousy, and that most music after that is uninspired.
But you know why? Because that was when I was 13-20 - the age-window when most people get the most into music and identify the most with it.
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