I am a mere programmer, not any kind of UX writer.

A company I worked for some 20 years ago had writers who mostly thought about the "happy path". When things went wrong, the error messages were left up to the programmers.

I discovered this when I tried to install our product on an old Mac and got this message:

Your hard disk is too small

Wait? My what is too small?

Later, on Windows, I got this popup:

You are not here

WTF?

I searched for this message and found it came from a function called CantHappen(), which was kind of like an assert(false). Something you throw into a code path just to note a place that you really know the code can never reach. Until it inevitably does.

I went on a rampage through our code, finding all these crazy messages and updating them - and when possible, fixing the code so the error messages wouldn't be needed.

My manager and his manager, to their credit, knew how bad our messages were, and they helped me pull together a little team with a writer and translators to fix these up. And we did. Our messages got a lot better, easier to understand and more helpful.

All because our Mac installer told me my hard disk was too small.

Great story and exemplar attitude from you and your manager! Too often such issues are eternally deprioritized, but you have got it into the pipeline and the team committed resources for fix. Ideally this should not happen, but that would require end-to-end collaboration of the entire team where UX people are involved on later stages of development process, adapting design and copy based on feedback from engineers. Many modern product designers just work based on „shoot and forget“ principle.