If open source projects like Slackware Linux can keep it stable on zero budget with a zoo of components since before we knew what SRE was, then Apple can afford to have operating system specialists who know the whole system. It’s like they gave up and welded the jukebox closed because it was making enough money.
Slackware Linux is way less complicated than MacOS. It runs far fewer, and much simpler, components and much less functionality in a default install. Like any Linux, there are myriad problems that can arise as users begin customizing the system, but until then, all those potential bugs remain deceptively hidden below the surface. And Slackware also has no constantly moving hardware team to keep track against and no hard timelines to hit for releases.