The previous commenter is technically correct— since slavery was already legal, the 13th simply carves out prison labor as an exception to the ban on slavery. And, as they pointed out, the legal distinction is important when it comes to individual states banning the practice of prison slave labor.
The constitution is a living document. Any parts found to be “problematic” were designed to be updated. Garbage like the 2nd amendment - especially- was meant to be updated. And the 13th…