Most of the engineers at those companies (and really all companies) don't work on those projects. Some people work on truly complex projects, but those people are a tiny fraction of the entire workforce. It wouldn't even make sense for a company to allocate people that way.
Also, I'd contest the statement that Google or Facebook works on the most complex software. They don't work in fintech, medical, hard real time that I know of (waymo does, but they've been spun out), and many many more fields of SW, HW and CS.
They work on hard stuff, but don't discount the complexity that other companies deal with.
i mean do you speak from experience or is this just more conjecture? what people on the outside fail to realize is that while individual projects might not seem complex (maybe frontend engineering on FB is less complex than pytorch) it's the scale of the systems you have to orchestrate that is incredibly complex.
Also, I'd contest the statement that Google or Facebook works on the most complex software. They don't work in fintech, medical, hard real time that I know of (waymo does, but they've been spun out), and many many more fields of SW, HW and CS.
They work on hard stuff, but don't discount the complexity that other companies deal with.