Technical debt is not about bugs, mostly.
Technical debt is about things like design quality and ease of change. High technical debt code is hard to change. That means that adding new features or fixing bugs is more expensive, takes longer, and is riskier. You pay interest on the debt every time you make a change (or don't make a change because it was too scary because your design sucked).
If you pay off your technical debt by improving the design, adding features and fixing bugs will be cheaper, faster, and less risky.