I do think music has declined, but it has nothing to do with the songs themselves but our (well more specifically Western) relationship to music. If you travel back in time to the late 19th century, music was a communal activity. If there was any large family gathering like a holiday, there was the expectation that there was at least one person who could play the piano well, one person who could play the violin well, and so on, and they would put their musical skill within the family gathering to play music. And even for people who don't know how to play music, there was always singing, meaning that it wasn't just one pianist wowing their relatives, but everyone creating music together, whether it's some hymn or some festive song or some popular music of that time.
The first treatification of music, if you want to conceptualize it like that, was the separation between performers and the audience. You now have one group of people who played music and one group of people who passively consumed music. One consequence of this was the decline in music literacy among the general population. I'm not saying that most people knew how to read music way back in the day, but most people would've at least intuitively understand what a chord progression was or what transposing a melody meant. A lot of songs just hit differently when you actually know how to play a musical instrument or actually tried to create music before.
The second treatification of music, was the creation of pop music that displaced folk music. Parenti made this point that pop music isn't actually popular music in the etymological sense of music of the people. Actual popular music is something like folk music. Some folk song that is exclusively played in a rural village passed on from generations to generations within that rural community is popular music. Pop music is just music imposed on the masses from the top by capitalists. In that sense, pop music will always suck and is supposed to suck. It's one means in which capitalist realism gets cultivated and spread.
The third treatification of music, was streaming services in my opinion. Most people understand on a basic intuitive level that pop music is worthless slop. Since the impulse to create music, like all other artistic impulse, is inherent in humanity, people will naturally try to get around pop music slop through the creation of indies. Streaming services are a monkey paw because a consequence of these services is that it can cater to a person's idiosyncratic tastes so well that it leads to hyperspecificity. The end result is someone has a hyperspecific collection of indies that no one else has heard of, leading to further atomization. It also propagates more capitalist realism, or more specifically, faith in the infallibility of the market. "Music is now better than ever because you can find all these good indies." That's faith in the idea that if a commodity is being sold on the market, the inherent qualities of that commodity will eventually cause it to take its rightful share of the market (ie good commodities will float to the top while bad commodities will sink to the bottom).
Does pre-treatified music still exists in the West? Yes. There's basically two musical traditions: one is religious music and by religious music I mean shit like Gregorian chants and hymns. They come packaged with their own bullshit that is pretty self-evident. The other is sport chants. I would say that sport chants represent the only authentic form of pre-treatified music that currently exists in the West. Sport chants are very much music even if they aren't conceptualized this way (and the reason why they're aren't conceptualized this way is because precisely sport chants haven't been treatified). The basic definition for what constitutes music is that it's an audio experience where rhythm is important. And sport chants very much have rhythm to them.
Sport chants are a completely communal experience with chants being passed down from generation to generation, they belong to no single individual but the people themselves, they are an experience where the performers and audience are one, there's a huge degree of physicality to it like everyone stomping on the stadium at the same time to create rhythm. It's an authentically human experience and no amount of weird chord progression and time signature, quirky juxtaposition of musical instruments, or topical lyrics from some indie no one has ever heard of will change that.
This is real music, and music will be good again when the rest of music gets back to the level of sport chants.
