The main thing people object to in slavery seems to be that it was racist. I wonder how the other aspects would play today, if the racist aspect could be fully and completely purged.
Would people sign up for slavery, if we could guarantee it were a multiracial institution with no race overrepresented, if we instituted strict requirements for clothing, nutrition, medicine, housing and humane treatment - a guaranteed decent standard of living, all you give up is your freedom? It'd be entirely voluntary: upon signup, slaves would first be sterilized, and owners would buy them from the government. It would be unconscionable to allow a generation of children born into slavery. That would ruin the market.
Would you choose a life of drudge work, no pay, no possibility of advancement, but at least you know you'll be clothed, fed, housed and taken care of? If you are like many people, you may already be choosing all the negatives from that list, pretty much. What price, hope?
One is reminded of recidivism. Prisons are drastically overcrowded and, we hear, dangerous places. And in case you don't know, people commit crime just to get back inside, where they know they're clothed, fed, housed, and to some extent, taken care of. Have recidivists been institutionalized - unable to survive outside? Or have they just found that for the less privileged, the outside has become a crueler institution than prison?