There’s probably a time axis that comes into play, at least for a large number of projects. Bad code which is immediately useful, even indispensable, can decline in utility fairly sharply the parameters which determine its usefulness change faster than it can be adapted to meet those needs or goals.

There's definitely a time axis that comes into play. I'd say that all tech debt should be (but probably isn't always) in that top left quadrant. Like they say, good/fast/cheap - pick two (if you're lucky).

Not useful code is always bad, because you never had to write it. It is just a waste.

Requirements change. projects pivot. Yesterday’s must have feature is tomorrow’s deleted code