I wouldn't say that anonymity is the problem here, but rather that social media sites are crafted to abuse the psychology of their users for attention, engagement, ad impressions etc.

It isn't a given that social media has to make teens depressed. If the psychologists and researchers that are hired by these companies to hone in on engagement were instead were paid to make their platforms less psychologically harmful, we could see better results. Hell, platforms have the potential to improve people's lives if they were optimized for those outcomes. Civil and criminal liability could be introduced to social media operators to ensure that their products aren't causing harm, as well.

Incentives to achieve those results can come from legislation and the judicial system.