Time is generally speaking a good filter for bad content in general. Of course most people are going to prefer older music to some extent because time typically allow for the bad stuff to get filtered out. It's not as if there wasn't bad music in the 80', 90's and early 2000's it just got left behind. It's also worth considering that music has gotten significantly easier to make and publish allowing anyone with a mic to make it and post it online. Obviously this is kind of like a double edge sword in the sense that as a result there's more good music but at the same time there's also more bad music. Add to this preference as well. Not everyone is going to like a certain song or type of music, it's impossible to point at a song be it popular or not and not have someone that dislikes it or that type of music. Music in general is very subjective rather than objective. To you it might feel like music has gotten worse over time for others they might consider it better.

Also this whole thing reminds me of the notorious "BORN IN THE WRONG GENERATION" Filthy Frank video.