What separates "working code" from genuinely good software?

Almost everyone who has written enough code eventually reaches the same realization: making something work is only the beginning.

A small project can often survive with messy code, duplicated logic, unclear naming, and a few hardcoded shortcuts. But as a system grows, those shortcuts start collecting interest. Eventually one small change requires touching five unrelated places, nobody remembers why a particular function exists, and debugging becomes archaeology.

So what actually makes software good?

Is it clean architecture? Strong testing? Good documentation? Simple abstractions? Performance? Security? Maintainability? Developer experience? Or perhaps the ability to keep the system understandable six months after it was originally written?