"But my boss told me to increase engagement at all costs, including substantially increased rates of teen suicides, so shrug guess I have to since my visa will be revoked otherwise and I need this cash to send home to my family."
Even when you cannot get highly employable US engineers to agree to do unethical work, you can always import some indentured servants who are too vulnerable to feel like they can say no.
I know someone that took a job at meta short term to get cash for a family member with cancer.
Go after the people giving the orders, not the workers trying to survive a deeply fucked up system.
I will never understand the framing of visa-sponsored workers at Facebook as indentured servants. These are incredibly highly-paid jobs, easily in the top 5% of earners in the United States even for fairly junior roles. Even in California, these folks are in the top quintile of earners. These are people who could earn a third as much in India, Canada, or the Netherlands, and still be living exceptionally well. They have exercised more agency than the vast majority of Americans or even Bay Area residents.
That said, expecting individual engineers to understand the greater context of building an online addiction machine is probably too much. The product managers and data scientists surface concerns and executives decide. And executives should be held criminally responsible in the event of gross negligence.