I'm a college age gen Z, and don't really think you can fix much with a social media ban alone, even ignoring all the implications if it's enforcement.
People don't get dysmorphia because some computer program told them so. The "influencers" are just other victims of a fundamentally toxic culture, or leaches on that insecurity.
You could say it used to be better before the internet, and maybe you'd be right. But all the internet enabled is just more people talking to each other about what's on their mind. As long as there are humans communicating through any medium, there will be a culture that can harbor these destructive tendencies, and the bigger more sparse that culture is, the more extreme its ideas can get.
Chronological feeds or more civic accountability for any algorithmic feeds (like forcing companies to share data with researchers to study their effects) could be a generally great initiative, but simply banning social media for anyone won't do as much as you'd hope.
Looksmaxing, the latest of these strange internet-induced mental illnesses, literally began on a phpBB forum.