Am I willing to take a 10% pay cut to work on things that are good for society instead of selling ads? Sure. 25%? Probably. But those aren't the magnitudes we're talking about. Total comp for a senior-to-staff level engineer at FAANG (or anyone competing with them) will be, let's say, 500k/year, plus best-in-the-world benefits. Total comp for government or charity work rarely cracks 100k, and even tech companies that are focused on good rather than profit, maybe 200.
And it's not like the FAANG jobs are bad - day-to-day, they're incredibly interesting. There's lots of fun stuff to build with smart people. The only problem is the background existential dread. It's also hard to argue that they're actively harming humanity in a lot of cases - maybe this line of reasoning works on potential Raytheon or Palantir employees, where the delta in morality is much greater, but convincing people to go from neutral-ish to good is harder than convincing them to go from bad to good.
So the question you're asking is, are you willing to take a 60-80% pay cut to possibly do a less interesting job, in exchange for moral fulfillment and knowing that you're helping humanity? You might think the answer is yes, but I think it's hard to fault people for whom it isn't.