People also want heroin. That doesn't mean it's actually a positive thing in people's lives. If anything the evidence is mounting that it is negative, e.g.: https://hbr.org/2017/04/a-new-more-rigorous-study-confirms-t...
I mostly agree with the rest of your post, though. I believe it's possible, though very rare, to work at Facebook and have a positive impact.
And there's definitely a total mismatch between regulation and the realities of big tech companies. I'm skeptical of government regulation solving privacy issues specifically (I think that stems more from a widespread cultural misunderstanding or unawareness of privacy concerns) but maybe it's needed for other ways these companies are negatively impacting the world.