A long time ago, music was very simple; then it became more complex (and therefore more expressive). Now it’s become less expressive again, which some interpret as "it sucks."
Up until the year 1000 AD music was only played with the seven natural notes (e.g., the white keys on a piano). The Bb note was "discovered" in 1025 AD in Italy. By 1450 AD, our 12 note scale was fully available on a piano keyboard and in some church organs. 7 white keys and 5 black keys that could be sharps or flats depending on the song’s musical key. By 1700-ish, Bach was composing all sorts of inventive things in new keys, including resolved dissonant suspensions. Stravinsky and others extended this to use dissonance without resolution. Erik Satie wrote a whole song composed of tritones ("the devil’s interval"). Each generation pushed the envelop.
The music of the 1920’s-1940’s used resolved dissonance, diminished chords to link key changes, etc. Think of anything by Hoagy Carmichael, like "Georgia on My Mind." Jazz just mixed all of this with the blues of Black Americans (which came from African microtonal music, which is why trills are used on the piano to approximate these microtones). Early rock and roll simplified things again, mostly to just three chords. It was considered by many derivative and trite compared to big band music, classical or jazz, but by the 1960’s (Beach Boys "Warmth of the Sun", Beatles "Because") musicians were introducing augmented and diminished chords, and changing keys. Jazz got experimental (Miles Davis, Dave Brubeck), rock got experimental (Yes, ELP); jazz-rock got experimental (Frank Zappa). All this exention of music was "inspired" more than "copied blatantly" (some things crossed the line, like "Here Comes the Sun" vs. "He’s So Fine", even if subconsciously).
There are a number folk-rock songs based on classical songes ("Blackbird" is based on Johann Sebastian Bach’s "Bourrée in E minor", Paul Simon’s "American Tune" based on Christian passion hymm "O Sacred Head, Now Wounded".)
Rap began in the 1970’s and the Sugar Hill Gang got the first #1 single ("Rapper’s Delight") in the genre in 1979. A lot of that music uses samples, which changed what it meant to copy someone’s song. Nowadays, many pop songs are assembled rather than composed. Songs like "Fantasy" by Mariah Carey are just a melody line added to a sample of the Tom Tom Club’s "Genius of Love". The "original" songs of the modern pop genre don’t have more than 3, or at most 4 chords in a song. There’s no tension, no resolution; just the same hook repeating throught the song... Drum samples ensure there is no variation in the beat, also contributing to the monotony.
The ears of 50 and 60-year olds remember that "golden age of rock" where songs were much richer from chord / key change perspective, or jazz. They appreciate that Guitar George knows all the chords. But to hear those strange chords, strange time signatures, etc., you have to go off the beaten track of listening. There are gems to be found, but they’re not in the industry’s factory of 3-note songs, samples, and other rubbish. Luckily, streaming provides access to a good fraction of those people who are just trying to make good music, rather than "be famous."
With so much music out there, I listen to what I like, and I always try to find time to understand some music that’s outside my realm of experience. Sometimes I like the new stuff... a lot of times, I don't...