At least we no longer have to listen to operatic sopranos a la Jeanette MacDonald, Kathryn Grayson, or Norma Zimmer.
Seems like progress to me.
Maybe, but if you like operatic sopranos you’re out of luck.
As for the quality of popular music getting worse or getting better, I only partly subscribe to “Sturgeon’s Law” (i.e., 90% of everything is crap). While there’s always going to be good music and bad music out there, I think the quality-to-crap ratio waxes and wanes over time. For example, a rich period in popular music like (roughly) the years from 1964 to 1971 will be balanced by a relatively fallow patch like the mid to late 70’s. Also, selective memories play a big role in someone’s evaluation of popular music.
Then it should be noted that music can become popular retrospectively, because the mid to late 70s were a rich period in their own right. Punk was invented, I think second wave ska came to the scene, and a lot of the seeds were laid for the explosion in styles that marked the 1980s. Just because it didn’t make mainstream Top 40 radio doesn’t mean it didn’t happen.
Heretic!!!
Popular music is definitely getting worse. In my opinion, the last great band was Guns N’ Roses. That includes Nirvana. I detest Nirvana. As far as guitarists go, Slash would eat Kurt Cobain as part of a nice Breakfast. 
I don’t think anyone would argue that Slash wasn’t a better guitarist than Cobain, but what does that have to do with Cobain’s songwriting?