Every Mac OS until OS X crashed continuously on even moderate use. Thankfully Steve did manage to build better systems at NeXT and brought that technology back when Apple acquired NeXT and was able to substantially improve Apple’s Mac product as a result.
It’s still far from “perfect products”, though, even during the time period that Steve was still alive and at Apple. To your point, I do agree that things have gone downhill quality-wise since his death, but I attribute this as much to being completely schedule driven as I do to the personalities involved in managing the projects.
And the question wasn't about a better platform or the vague "greatness", but the myth of perfection, the one where serious bugs unfixed for years should be enough to dispel