That's somewhat of a strawman argument: if you think dealing crack is the same as dealing human beings, where do you even draw the line? Is it not OK to deal in anything, on the basis that it could be a human being if you changed it to a human being?
The difference when dealing a human being is it's no longer a transaction between only Alice and Bob. There's now a third person involved who has every right to object to the transaction. Decentralised marketplace or not.
"Both" of these problems? The problem is dealing in human beings, right? What's the other problem?
Am I proposing that the tools to solve human trafficking go away? I wouldn't put it that way. Lots of societal progress comes with trade-offs. There will certainly be challenges for law enforcement but I'm confident they'll solve them.
The world isn't going to descend into a chaotic state of everyone buying and selling everyone else just because free-trade becomes ubiquitous.
The OP said "Can we find a way to help law enforcement police at the very least the really, really bad stuff," I think you're eliding his entire concern when you just say "I'm confident they'll solve them"
The difference when dealing a human being is it's no longer a transaction between only Alice and Bob. There's now a third person involved who has every right to object to the transaction. Decentralised marketplace or not.