Most artists these days self-distribute via platforms like Distrokid, not via a label. Distrokid just passes along streaming revenue, so they don't have any incentive to fight for it. And obviously, artists aren't in any position at all to collectively negotiate - you publish on Spotify, or you're unknown. The fault does, in fact, lie mostly with Spotify here.
According to the data I’ve looked at from Spotify, the big 3 labels are about 63% of their music, Merlin (which includes some actual small labels but also things like distrokid) is about 15%, and then there’s the rest. So the majority is the majors, but the other artists certainly could negotiate collaboratively if they wanted to.
