To piggyback[1], agency discussion are orthogonal to affecting outcomes.

Shifting responsibility typically justifies outcomes rather than making meaningful change. It resolves the cognitive dissonance between a negative outcome and inaction.

If one is actually interested in improving the negative result, it doesn't matter what their personal relation to the cause is. The process is simple: make meaningful change to to the system that causally proceeds the outcome.

In your example of obesity, personal responsibility is meaningless if one's goal is to decrease it.

Same with the negative effects of social media. If you care about the consequences, personal responsibility's only effect is to make one ok with inaction.

1. Intended