Facebook is a mirror, and a magnifier. "Fixing" FB is, at best, curing a symptom. A general lack of critical thinking is not FB's fault.
To promote otherwise is naive and dangerous.
No doubt humans are flawed. But is that FB's fault?
That everyone has self destructive tendencies is pretty clear, it's only when you get a reward for following through with them that you have a problem.
That the reward is likes or drugs is pretty immaterial.
Are you sure about that?
If the government and parents are failing to prepare children for dealing with the adversaries that they encounter in life ... does that mean anyone who is using that lack of preparation to their advantage while knowingly hurting those under-prepared people cannot possibly be at fault for their actions?
If a child hasn't learned about the dangers of drugs in school or from their parents ... does that mean that someone selling them hard drugs cannot be at fault for making money from that situation?