Music isn't getting worse. Popular music has always been mostly garbage, and the further back in time you go the less garbage gets remembered. There's always been enough music for the good stuff to still make up a large body of work once you filter out all the trash and so music seems to get better the further back in time you go (until you go far enough back that recording quality was bad.)

Combine that with everyone of course always having the most nostalgia and exposure to stuff that was around when they were teens and you get everyone saying (time when they were a teenager) was when music was good.

All you need to do is stray a little outside of the top music charts, check out local gigs from lesser known artists, explore specific genres you like and you will find so much good music you won't be able to listen to it all.