Artists should be mad at the labels THEY entered into contracts with, not spotify.
The labels have a monopoly on talent and content, It's impossible for anyone to make significant money in the streaming game when they have a stranglehold on the supply.
[0] https://pitchfork.com/news/apple-music-in-contrast-with-riva...
It certainly pays per stream in the sense that if an artist has 110K streams, they get 10% more money as if they got 100K streams.
It may be the case that the amount per stream varies a bit depending on which label you're associated with, or what Spotify's subscriber numbers are that month. But that still doesn't change the principle that your revenue scales linearly with streams -- that you're paid by stream.
Or am I missing something?
Not the artists with "most" streams. Record labels still dominate the market.