> world did fine before derivatives

The Hittites and Bronze-Age Egyptians had forward-deliverable contracts that, if you squint, they would trade amongst each other. The idea of being able to assign a contract to a third party to which you're a beneficiary is about as old as civilisation. In part because it's obvious. In part because it's impossible to police. But mostly because it's useful.

(I'm ignoring insurance and reinsurance, both of which are derivatives and rely heavily upon them.)

The scale of things was much different back then. Not comparable.