Oh, a very good point. And I agree with the term being problematic, especially when contrasting with references to ‘traditional cultures’ and indigenous people, the use is not appropriate.
For our fediverse “community-driven” as @jorge suggests is a good one. I would avoid “ethical social media”, because this is too abstract and things that happen on fediverse are not always necessarily ethical (even though we strive them to be so). “Genuine social media” is one I like, where you can be yourself, and express “true social”, not the plastic, artificial kind.
But what implicitly derogatory term to use for existing social media? 
I don’t think “mainstream” cuts it. In its original meaning it is common, normal, widely used. And in culture wars and divisive politics it is given negative connotation (“the MSM”) with an agenda that is not appropriate for a fediverse we’d like to see, imho.
“hegemonic” may cover how we feel about the other social media, but it assumes also a lot of background knowledge to understand why it is used. Knowledge that I think for the most part does not exist with average users of such platforms, and doesn’t put it in context. Then it is just a strange, bit academic word to them.
“Commercial social media” may be used, as anyone knows what the addition of that more or less means. It may raise the additional question “Why? It is free, right?”, which is a good one to ask. Many people also don’t like things to be commercial, though another part just wouldn’t care.
(Btw, in advocacy I started referring to Big Tech as “Advertising giants”. Like when someone says “Use Google [This and that]” I ask the simple question “Why whould you host your service on the biggest advertising platform on the planet?”. Most people think of Google as some standard part of the web, that is freely provided to them.)
Toxic, exploitative, abusive … all accurate, but communicating a lot of political bias that may trigger resistence.