Let freedom ring!
When it comes down to it, you're right.
I think back in Mumbet's and Jefferson's day, slavery was still an idea that, although you might not be able to be born into it, slavery, as punishment for crime, or perhaps just wanting to sell yourself as a slave for some reason, was possible.
But I'm sure we have come very far since then. Oh, very very far. Perhaps in some strange directions, but in the end, you're right. We need to re-establish the 13th amendment to ensure that it is neutral in terms of who it targets as to whom is immune to being a slave, and also, it must be made impossible for a slave to exist in America. The moment your littlest toe touches American soil, the chains are broken. You are free.
And thus, we must understand what a slave is, and how to define it very accurately. Because I certainly don't want to be a free person forced to work for faceless masters in exchange for cheap bread and filthy water, to be housed in a small hovel.
No, I would rather build myself a garden, I would rather filter my own water, and I would rather work for myself, or perhaps with a business, in order to build wealth.
What a slave is in the modern day is not someone who is wrapped with chains and whipped. No, it is more subtle than that, and it is the subtle definition that we must respond to. Lest we wind up back where we started! Slaves to a king.