>Useful middlemen do serve a role and add value. A parasitic middleman just extracts value without adding any value anything in return.

And do tell how you distinguish "useful middlemen" from "parasitic middlemen". These are meaningless terms based on your own value judgements. In other words, they're completely useless in practice.

A universally recognized transaction-coordinating mechanism works much better. And guess what? We already have that: price.