they aren’t saying the modern worker has it just as bad as other slaves, they’re talking about institutionalized forced labor.

I’d also like to mention that anarchists and socialists have, for a long time, criticized wage labor under capitalism as being more exploitative than literal serfdom i.e. kropotkin’s “shame on the feudal baron” quote. Serfs giving up a quarter of their crop was seen as barbarous, but wage laborers give up the entire value of their labor and are paid only a pittance for it