It being legal doesn't do much about its unfairness.
> For the average person who can maybe comfortably afford $90 per year, a subscription service is a much more viable way to support the musicians they listen to than buying 4-9 albums
The option that you describe as the best for people who can't put more than 90$ a year on music (which is perfectly fine), is going through a subscription service, because even if a lesser amount of that money goes directly to artists, more of them get to see a bit of it.
I disagree with that, because you don't know for sure where your money is going, as all of this distribution system around streaming services is pretty opaque. As far as I know, the money from subscriptions on Spotify is not equally distributed among the artists that a user listens to. Bigger artists tend to get more per play than smaller ones.
The other option would be to spend that same amount on buying albums each year on a service like Bandcamp, which is known to distribute the money in a more direct and transparent way, and where artists actually have more control over what and how they want to sell.
It definitely means making a choice about what to buy, but it is still better than letting an obscure algorithm make that choice for you.
We should also consider that we can favor artists who are in need over those who are already earning large amounts. This is the opposite of what streaming services seems to be doing.
> your idea that poor people should have reduced access to the arts
This is not my idea and I didn't say that. I criticize those who waste their time chasing the "theft", who they blame for being the origin of the artists being poorly paid, when the subscription model being proposed as the best solution is actually far from it and could also be considered as theft when you put out the numbers of how much artists are asking for their work.