Coming from the finance world here... Maybe the problem here is more how money is a societal construct, not a technological one, even though it can be represented technologically. With all due respect, people like Marc Andreessen seem to think that the constraint here is a technological one, when the technology to do a lot of what they're talking about has been around a long time. It's that, for non-tech related reasons, people prefer things working a certain way.

I can see things like blockchains improving back office settlements and clearing, sure, but... whatever?

Disrupting the actual financial system is nothing short of disrupting how society who gets what, and what gets done. This is not a technological problem you're dealing with.

No, they (currently) do not allow debt. Why is specifically debt related to disrupting ?