The more life experience I have the more I conclude that assessing the existence and extent of someone's fault is a pointless exercise. People tend to exhaust enormous amounts of pointless energy stuck in that place.

Your last sentence drives it home. They deserve compassion. Who cares about subjective assessment of fault once you reach that conclusion?

Largely agreed.

To your last point, people who believe having an internal locus of control is useful for preventing (not necessarily treating) addiction.