I don't have a personal problem with slavery. The issue is typically a conflation between chattel slavery, voluntary slavery, and penal slavery, and their various applications. Chattel slavery where the slave has no rights or say in ever having become a slave is pretty much universally immoral. I think voluntary slavery made sense back in the day. Whether it be by indentured servitude, being an in-home servant to a Lord, or what have you. Or military service nowadays. Penal slavery has pretty much always been a thing. Still happening now. People don't seem to mind it that much.

Ahh, apprentice slavery was another things back in the days.

That's why it was, quite literally, *master* and apprentice.

You were your master's slave in the hopes of learning the job and becoming a tradesman yourself in the long-term payoff.