Even if you feel like it is impossible to leave Facebook, the truth is they make most of their money from ads served while you are in their ecosystem. Just spending less time on their platforms is good for you and good for reducing their relative power in the market.
We are all better off in a world where Facebook and Google face an economic harm if they abuse their monopoly power. I don't think consumer action is the best way to cause that harm, but it is the way that is available to everyone on this forum.