If your “throwaway” code works fine in production for years without any active maintenance and the only down side is that it needs a rewrite five years later, was it really that bad? Or is it the exact thing tech debt refers to - borrowing future time to work on what’s important? If I had to make a point it would be that there’s no line between code that needs to be replaced right now and code that is perfect and lasts for decades - it’s a spectrum and circumstances influence your tolerance.