Well, today's society isn't that far off from slavery. The main difference is the lash has been replaced by economic punishments. People have the gall to call work voluntary when you literally starve if you opt out. Most workers will not see much improvement in their quality of life despite working hard for long hours.

We'll be free once our basic necessities are taken care of unconditionally. That means food, housing... Everything needed for a life with dignity. Until then, we are slaves to the current economic system whether we want to or not. We are not in a position where we can say "no, I don't want to do this anymore" without serious consequences.