I'm not so sure. A lot of art comes out of "affordable areas" — sometimes small college-town ghettos like Athens, Georgia, for example. Why couldn't we get a Philip Glass from Manhattan, Kansas?
Most artists that try to invent something new start with essentially no audience. They don't create that for the big bucks.
What I have noticed of this, and my readings seem to point to the reaction of people around someone in an uncharted direction like PG being a mix of "bemused but admirative and encouraging", and "ignored". And what proportion of the "peers" is now online? IG and such? (For an artist in my life, IG seemed to be an essential lifeline. A main connection.)
And they can all post videos of performances on YouTube. You don’t even need to have an orchestra perform a work for an extended time before you can find an audience. I would think that this would make it more likely for new composers to be able to find success than before. You don’t necessarily need to be in an NYC or Boston like before.
Congratulations-- you're officially wrong on the internet!
Meet Harry Partch:
https://en.wikipedia.org/wiki/Harry_Partch
He roamed as a hobo for years during the Great Depression. The text for Barstow is graffiti that he saw scrawled on highway railings during that time. It's featured in most music history books that cover the 20th century. (Also, many of the instruments he invented are visual works of art, in addition to being musically beautiful.) And if you liked the recent HN article on just intonation, well... let's just say you're gonna love Harry Partch!
There's also Conlon Nancarrow, who got pissed at the U.S. harrassing him when he got back from fighting the fascists in the Spanish Civil War. He moved to Mexico City and hand-punched player piano rolls in seclusion, for decades.
Other composers and musicians made pilgrimages to his studio, just to hear what it sounds like when, say, a 12-voice canon has each voice moving at different tempo.[1]
Nancarrow received the MacArthur fellowship back in 1982. At one point there was a piano duo who taught themselves to play a selection of his pieces as a four-hands duet for one piano.
People who care about music will find interesting musicians, no matter where they live. This goes back at least to J.S. Bach, who reportedly walking hundreds of miles to listen to Buxtehude improvise at the organ.
1: and what are the proportions for the voices of that canon? You guessed it-- they're the ratios from a just intonation chromatic scale, which Nancarrow probably got from a book by Henry Cowell (New Musical Resources, IIRC).
Edit: typos
The commenter remarked "we would never have heard of Philip Glass." Who among the laity would have heard of Philip Glass and the people you listed? I expect that Venn diagram is really two circles.
> People who care about music will find interesting musicians, no matter where they live
This is the 'just world hypothesis' and survivorship bias combined. Some very talented people will be discovered despite their circumstances. An enormously larger number will not. You won't know you don't know them.