I’m with you on most of that, but there is a lot of excellent music still being made that you’ll never hear on the radio. The death of radio was at the hands of the consultants who fill the playlists with bland songs that are focus-grouped to death. My best source has been YouTube because I can play one song I like and let autoplay take over; I often fall down the rabbit hole listening to artists I never heard of.
But I'm constantly discovering new music even as I approach my late 50s. As you point out, you'll never find it on terrestrial radio, which are basically the same 300 songs over and over again with about 32 minutes of chit-chat and commercials every hour.
There are many ways to find new music such as Pandora and other similar apps that take songs and bands you already like and feed you newer songs based on them. But for me, Sirius/XM is the best as it's commercial free and focused on the music in every conceivable genre. I have about 30 of those stations in my favorites. Best ones for discovery are Spectrum, Outlaw Country, Garage Band, Loft, and Deep Tracks. But even the ones that you would think are limited, like First Wave, Yacht Rock, 80s, Classic Rewind, etc., go pretty deep and I'm always discovering new music from the period of my youth that I somehow missed while growing up.