Slaves can be bought and sold. Their children can be bought and sold. Slaves can be physically punished and even killed without legal recourse. They have no rights. They are property.

And it still exists, so the modern equivalent of slavery is still slavery.

What you are talking about is the social obligations of being part of civilization. Yes, there is no free lunch. We must all work to live unless someone else is willing to foot the bill for us. But if that is slavery, then literally everyone in the world with a job is a slave and the word loses its meaning.