I do think it is worth considering how social media effects people at a more granular level. For instance, I think the focus on "engagement" probably makes the negative effects worse, and we would see less negative effects if social media companies weren't optimizing for that.

However, my understanding is that Haidt wants to completely kick kids off of social media. This is a bit different from how we engage with opioids, which are still used for pain management. Opioids only really have positive effects for pain management, and so I think that it is reasonable to keep them regulated. (although I've heard grumbling from doctors about how them trying to be careful about who they give opioids too leaves a lot of people in severe pain) On the other hand, social media's positive effects are things like staying in touch with old friends, building community with people like you when people around you hate you, and learning new skills. I don't think that restricting or eliminating social media use will help here. Instead I hope that people take the design of social media more seriously. (for instance, HN or Mastadon)

EDIT: additionally I'd say that the negatives of unregulated opioids do far outweigh the positives, which is not the case for social media.