Historically, the group wasn't making a whole lot. Now, some of them are doing well with things like Patreon and YouTube monetization, as well as selling through streaming services.
Those routes weren't readily available to them while production, distribution, and advertising were largely controlled entirely by the big production houses. Now, the independents are able to produce qualities on par with the larger houses and able to reach the same audiences.
So, numerically speaking, they've probably benefited much more than the folks on the major record labels. They are no longer just playing for 50 to 100 people in a bar, they are having their music listened to by that many people in an hour, across multiple streaming services, and making a few dollars they'd have never had the chance to make, even thirty years ago.
One of my friends does nothing but make music for online distribution. He's developed quite a following. He doesn't even have a garage band, he makes all of the music himself in a spare room in his house. That wouldn't have been an option, just thirty years ago. Even a decade ago meant he still had a regular job.
I imagine there are many similar cases and that, in aggregate, the independents have benefitted far more than the major studios - at least proportionately in terms of growth.
Don't forget sale of merchandising. If you can gather a bit of a following on YouTube, even if the monetization is still low, you might be able to make a decent income just selling personalized caps and tshirts online.
Thanks! I hadn't even thought of that for people who don't do live shows and only do online stuff.