I'm using MacOs/OsX since Lion, and I can say that it was very stable (even on my Hackintosh) and I observed stability issues increasing with all the following versions (on real Apple HW) and I'm on the same ship as GP never upgrading to newer versions until at least 6 months pass.
Yeah, first few OS X releases were famously buggy as they were figuring this UNIX stuff and the OS 9 compatibility, but they stabilized about 10.4 Tiger.
Honestly the OS X itself (uhhh macOS now) is still fine, even with Big Sur and its weird iOS controls, however the other software is sometimes weird; but - let's say Numbers was never good and iWeb was always downright bad. And iTunes was bad in Jobs era and is still bad (as Music).
I however still kind of miss when native Cocoa apps were sort of good and not just ported iOS app via Catalyst or something. But whatever. I'm old I guess
When OS X came out 20 years ago, it was the star of the show. Nowadays it's just an annoyance that Apple has to keep around. The quality has demonstrably fallen, and the internal struggles it's had within Apple have already been documented.