fwiw, understanding was never really the goal. calling it "debt" assumes all of it needs to be repaid, but most of the time this just feels like brain OOM. imo the skill is knowing what actually needs to stay in your head.
It seems to me that assuming that debt needs to be repaid was moved to a footnote during the ZIRP years. I feel like there was a shift of the poles, the movement of a rift, you get the idea.