I have a theory, that the "FANG" companies pay such high salaries in compensation for making those devs implement shady features that are harmful to everyone except the bottom line of the company.

It's hardly a theory when the converse is plainly true.

Look up similar jobs for academia, government, or NFP/Charities. They're (on paper) driven by their mission, not by profit, and the salaries match that goal.

There are countless low wage engineering jobs implementing shady features. Any random consulting / agency works on such products too.

If that\s true then those devs should not complain if people attack them verbally over it - that\s what they are getting paid for, right?

The joke here is that the majority of FAANG engineers are actually doing anything but saying "I'm blocked on" every week.