I'm assuming the TOS you originally agreed to had a clause that is something like "we can unilaterally change this." So, you could I guess check the TOS when you are making an account, and only use sites that don't have a clause like this. Likely this will significantly reduce you selection of social media sites... this just seems to me to indicate that investing too much effort into improving social media communities is not a worthwhile endeavor (or, maybe you find it to be a fun hobby, so just do it for fun and don't expect any payback).

Realistically most sites want to exploit people like you.