I know a solid number of FAANG and ex-FAANG devs -- the stuff they work on (from what I've heard) isn't much different from the sorts of software I assume most people in SaaS startups work on. Outside of scale (which is significant). A lot of it is internal tooling though, which never hits absurd amounts of scale.
I do know that there are x100 devs at FAANG that put out the groundbreaking projects that change landscapes -- but that's generally these well-known outlier developers for which there are a tiny handful in the world.
HFT and quants I understand, that's money-printing business, FAANG I don't. But also, I've never worked or applied at FAANG, so I can't really form a valid opinion I suppose.