> so too has the sheer volume of rare, underground jewels
This. As for discovery, it's never been easier to find things by oneself. Bandcamp (nice place to bootstrap rabbit holes), Spotify artists playlists, Youtube channels, Subreddits...
The Fantano phenomenon puzzles me. I have tried to watch his videos, but they're so boring. He looks into the camera for 10+ minutes just talking.
There are never any cut-aways, or song clips, or on-screen graphics...anything to reduce the monotony. And yet he has a million subs and the comments section does include discussion of the record. It's not very deep, but it does exist.
For me though, it's too boring. I'd read the review if he wrote articles, but definitely would not watch.
That is to say -- I've found that while the sheer volume of mass-produced crap has gone up (including but not limited to music criticism), so too has the sheer volume of rare, underground jewels. I don't know if/maybe doubt discovery has been cracked yet.