The volume of music available for an average person anywhere in the world to purchase today is many orders of magnitude greater than any era in the past.
You're grossly mischaracterizing this.
> recorded a track in their garage in 1977 and sold a few cassettes to their friends
To be fair, so was Reaperducer, with the "Only if your taste in music is very narrow" bit.
You are 100% correct. But not for the reasons you imply. Music recording is just barely 120 years old, and mass market music media sales are, perhaps 75-80 years old.
And since many of those recordings are still around, with more music being recorded every year, it's no wonder there's more music available now than there ever has been.
That said, Sturgeon's Law[0] applies to music as well as everything else.
Found this out when I was adding Johnny Winter / Guitar Slinger to the collection and noticed it was blocked for sale. https://www.discogs.com/release/3318469-Johnny-Winter-Guitar...
Nope. Not even remotely. Only if your taste in music is very narrow.
Just this weekend I tried to buy some Christmas songs that were popular and common on the radio in the 80's. I could only find about half of them on Amazon or Apple Music.
Most had some version available, but not the canonical one I grew up with. Some didn't exist at all.