I don't quite agree with the 'for anything'. For poor/missing technical assets that area direct cause of insufficient upfront investment (of time, money, etc),

I don't quite agree with the 'for anything'. For poor/missing technical assets that area direct cause of insufficient upfront investment (of time, money, etc), that's 'tech debt'. Missing/outdated docs/tests? Tech debt. "Low skill with technology" - probably not as easy to lump it as 'tech debt', imo. "Lack of understanding about the problem" - again, doesn't seem like tech debt, but... business debt. Tribal knowledge debt. Operational debt, but not explicitly 'tech' debt. But... perhaps that's your point? It's easier to just say 'tech debt' for everything, even if it's plainly the result of underinvestment on non-tech things?