It’s stable in the way that a person taking small predictable steps at a time is stable compared to somebody who making large random lurching steps. Sure, the system is often changed, but if only a few packages have changed, should there be a problem it is easy to identify the culprit.

Although it is hard to say. Ubuntu also has, I guess, intentional behavior that is hard to distinguish from a bug, like packages switching from apt to snap. So it might just be that my subjective experience feels more buggy.