> It's not debt. It's stuff that used to be perfectly fine and due to no fault of yours is not anymore.

The risk of this happening is more or less measurable and is the debt. Denying responsibility doesn’t make the debt not exist. It might mean you’re so far removed from understanding how your (sub)systems function that you’re unable to assess it. It may be so complex that no one is able to quantify it, in which case I suppose “it doesn’t exist” might be accurate enough — either your business fails or it doesn’t based on the success of your subsystems, and your business outcome is the measurement. I’d rather have someone else be the measurement.