>a new hire is always an unknown factor by definition.

sure, that's why the entire hiring factor is an industry comprised of HR, recruiters, and hiring managers. you're supposed to minimize the odds of a bad hire. Similar to any other business that is an unknown factor until you do research.

Life's all about dealing with known and unknown unknowns.

>And if you aren’t FAANG, people usually aren’t lining up at your door to work for you, so you have to make do with what you get.

Not in this current economy. That's part of the frustration with the current market. Everyone is lining up, few are getting hired, but hey it's okay unemployment is low and the economy is great!

>Pair that with the fact that the new hire won’t reach full productivity until at least 6 months in

well that's also mitigatable. Make your process public and let candidates study to your tools and process. But that will never happen because it's more important to hide your process from competitors than get qualified candidates to ramp up quicker.