You make an excellent point on the 13th amendment.
I would quibble as to whether a person wanting to be a slave (I’m talking about biblical slavery) is a rarity. I rather doubt it. Many people who, for whatever reason, just have a hard time coping with basic life decisions would love to have a kind master making all those decisions for him/her.
I’d wager that if we actually allowed time-limited, specifically enforceable labor contracts (perhaps with a few other protections within the biblical spirit) we’d have quite a number of takers.
I hope you are incorrect as to the number of people who would go willingly into slavery. A nation of slaves is not to be desired. However, I fear that your view may be closer to the truth.
I pray we never test that view.