I think you're missing a few relevant things:

An annual spotify subscription in the U.S. is $99 (possibly less with boxing day deals and such), but I'd assume the majority of subscribers are outside the U.S. where prices are lower across the board.

But 6M of those artists may be AI-generated filler content, possibly published by bots. I don't think the correct idea is to divide the potential money people can spend by the number of artists. There should be some connection with what people are actually choosing to listen to, anything else would reward opportunistic publishers of low-effort, uninspired music (and encourage people to do even more of this).

Which then brings up the problem: If people were to fund one artist they listen to (lets say an artist they choose to listen to rather than an artist they accidentally listened to a song by once), are they going to choose at random from their list of such artists? How do they then get that list to pick from? How do they discover new music to potentially listen to more of in the first place

Apps like Spotify, (or OSS like YouSpot that piggybacks on Spotify) are both valid answers to those questions.

Then you have the dilemma of who's paying the cost of the bandwidth, and the development costs.

If you want to be fair, I think people should be encouraged to pay what they comfortably can with their budgets. They're using the infrastructure and platform of spotify (or similar) for discovery, so Spotify or similar should reasonably expect some money to cover costs and pay their devs. Then they can also pay any number of random artists whenever the mood strikes them.

If they can't afford spotify, they can still use YouSpot, kick the YouSpot devs one or several dollar per year, and then purchase music from their preferred artists up to the amount comfortable for them.

Using YouSpot is the closest actual thing to 'stealing' btw, because they're actually consuming a resource (bandwidth and server time) that's intended for subscribers, from a company that pays for it. Add to that, by using their software (and spotify's upstream), if they're not financially supporting the YouSpot devs and the Spotify devs for the work they're consuming then we're back to the initial claim (which I already said I disagree with) that consuming something that can be 'copied' ad infinitum without paying the producer is theft.

But I think any of the above are reasonable options for people who want to maximize the support of creators of the things they consume while staying within their means

I mostly listen to long-tail artists, so if I were to pick one at random, it would probably be in the 80-99.9th percentile group. (Assuming 80% of Spotify's catalog is spam -- that could be, but I don't use Spotify, and have never encountered spam any of their competitors).

This would pull some revenue away from the > 99.9th percentile artists, but that's OK with me.

I'm more worried that, even if we count jobs that are way below minimum wage, Spotify is only supporting 15K bands worldwide. That rounds to zero when compared to their listener base and their revenue.

Anyway, I pay more than just a streaming subscription annually, but I went with an estimate of what's going into just Spotify for my calculations. I'm not convinced there'd be much societal impact (in terms of artists not being paid) if they disappeared tomorrow.

Then you're probably the rare exception who would likely benefit independent artists more by just randomly picking a few every year.

If everyone just pirated and picked a few musicians to support directly every year, the overwhelming majority of people would pick from the 16,000 in the 99.8th percentile on spotify, and the majority of the hundreds of thousands of artists in the 80th - 99.8th percentiles would see no income whatsoever from digital distribution.