This was what I was waiting for in this thread.
Most claims of music being in decline are pretty much hacky in character. It's something we intricately try to figure out (why it's experienced as such, and whether there's anything substantive to it) in musicology.
I know the usual suspects as popularized on YouTube; the loudness war, claims of harmonic simplification, structural simplification, faltering skill in regards to musicianship. To those in particular, I'd point out that good loudness (that is, well sounding compression) is hard to do; for the simplifications the claimants of this usually swear by blues and/or classical that are incredibly formulaic, which usually undermines that position (classical harmony and structure is much more limited than most people realize); and there is real skill demanded in using a PC to compose this stuff.
Some of the claims of music in decline use the skin of empirical research to provide their results, but I'd like to stress the principle that particularly in the case of art, what measurements you use for it
really are in the eye of the beholder. There was a viral study that was popularly read as decline of complexity in sound, for example. How one sided this study's points were... Depends on the reader. I read it and it was much less grumpy old man than it was represented as in the media. It's strue that certain elements have been less prioritized, but it doesn't mean other things have been emphasized for the benefit of some vision (which is, yes, usually capitalist in intentionality more than anything else. There's a correlation between capitalism and sound in a material way, but it's usually more complicated than "decline"). It's basically the equivalent of the OP point: There's stuff in newer music that older ears are usually not able to detect.
This channel is also pretty good usually, but did a ridiculous claim about classical music vs. pop, where they noted that classical tended to do slower buildup in harmony, and pop structures, particularly four chord arrangements, basically gave the climax once every four chords. Thing is that this only holds true if you use function harmonics as a strict base of your perception of music (pop has buildup, it's just not expressed in intervals, usually), and necessiate
this classical particular form of buildup as integral to musical quality, because otherwise you can't claim decline or lack of quality. (That classical actually has plenty of pieces without Wagnerian/Beethoven-esque buildup also demonstrates why this whole idea is ridiculous, but let's leave that be for now.) If you don't spend the whole piece building towards a proper harmonic cadence in Western classical, your piece has
failed. So if you use that premise for every kind of music, a lot of stuff is just going to be
failed art. No matter what other stuff is done there.
It's like, think about if you go into a forest with the intention of biking on a bicycle route. Following this, you believe it's a bad forest if there isn't a bicycle route. You don't find a bicycle route, it's a bad forest. Maybe the forest has other uses than biking, and using a biking measurement for it kind of misses the other ways you can engage with the forest.
Translating that, of course any kind of music is going to be "in decline" if you judge it by unrelated harmonic rules and modes of perception. If you don't have the mode of listening for certain signs. I know the idea of thinking the forest is bad for not having a bicycle route, even if you're a biking enthusiast, is absurd. But that's the usual problem when people claim stuff is in decline. "It doesn't have this old harmonic rule anymore! It sucks!"
I also know that a lot of people swear by having more complicated harmonies that "don't follow rules" or whatever. But... Let's just call it avantgardism, and point out that this is also a poor universal metric, to claim that things must always push forward. It's a metric as much as a stringent harmonic rule to just believe that rules must be broken, and simply doesn't apply to everything. Old ears can have the issue too, of embracing avantgardism at the cost of everything else.
I actually have this problem in regards to a lot of genres. My ears simply aren't in tune with presuppositions of signs that exist in certain genres of music. Which is why I keep to my own ballpark when studying music.
