I don't think your random FAANG worker could show up somewhere and just "build the right tech" on their own, especially in a not so good team. There are some very strong SWEs, but the average one isn't a super star. My experience working at a FAANG is that everyone in my team is good (able to solve problems, hard working, good foundational CS knowledge), and there may be 1-2 very strong ones who really make things happen. Also, a lot of the skills we develop are with our own internal systems, I don't know how easily it would transfer to open source world.
In my previous company, there were some good engineers, but also some mediocre ones. This led to a lot of bikeshedding, wasted time trying to convince people, to review bad codes and so on. What I'm trying to say is that a very good engineer may not be able to unlock their potential in bad team, unless they also have good leadership skills.