OS X and iOS are both way more stable than any pre-OS X Apple OS. I can't believe people forget it.
When people talk about OS X having issues, they often mean some new feature is a little flaky. Classic Mac OS lacked basic stability and security features like preemptive multitasking and memory protection. Classic Mac OS was just like the pre-NT Windows: crash prone.
That's not a high bar though. The only other high profile desktop OS around at the time, Windows NT, was more stable than any pre-OS X Apple OS for a long, long time.
When people talk about OS X having issues, they often mean some new feature is a little flaky. Classic Mac OS lacked basic stability and security features like preemptive multitasking and memory protection. Classic Mac OS was just like the pre-NT Windows: crash prone.