We must be using different FAANG software because the ones I use on a daily basis are slow and buggy as all hell. The last few versions of macOS/iOS have been atrocious. Every version of CarPlay I've used has bugs. Amazon apps are full of glitches. Compare that to developing engine ECU software which I think is a far more difficult engineering task that the average overpaid UI JavaScript slinger could not handle. You can't just update ECU software every week because you sloppily overlooked something. Unless you're Tesla of course.
I don't deny that there are many outstanding, technically excellent engineers at FAANG that deserve every penny they make. But the sad reality is many of them are just TC-chasing posers who got lucky and have subsequently deluded themselves into believing that whatever narrow expertise they now possess is worth far more than it is on the open market.