...isn't it also possible that music has gotten worse in this generation? Maybe even over several generations?

Age is a factor, but not the only one. I've heard many teens say they hate "current" music, and they prefer music of earlier decades (60s, 70s, or 80s typically).

There are definitely changes in mainstream pop music. There are studies showing how it's gotten simpler and simpler in terms of harmony, melody, lyrics, etc. Of course, simple alone doesn't necessarily mean bad...

Another change is prevalence of explicit, obscene, vulgar language in pop music. A lot less romantic music and a lot more f-bombs. And a lot of rage and meanness. Almost everything on the pop charts. That is a radical change. That alone turns me off to most new pop.

Another factor is disappearance of music education in public schools. This affects both musicians and listeners.

But I do find plenty of great new music; it's just not likely to appear on the pop charts. It requires more digging around.

So the "old" people may be both wrong and right....