But then we are back at the original problem, which is that I have no ability to repossess a nontrivial amount of property to handle a default and this system is explicitly constructed to be outside of the bounds of things like credit scores.

Regarding the auto financing. Traditional lenders will typically have no ability to repossess secured assets themselves, they will send out a colourful letter and if that doesn't work, sell the debt to a collection agent. DeFi in the form currently available doesn't need a credit score as it is secured against collateral, but a credit score would likely be needed in this case. New cars sold in the EU are likely trivial to repossess; I believe they have built in location trackers.