While the risks you bring up are valid, many of them are not new but amplifications of preexisting ones. In the past, children have largely managed to navigate these on their journey to adulthood. An unsolved problem with social media: it's an amplification of parking lot scuttlebutt. It will entice you to see catastrophe and share it with others. Perhaps despite your position on this, you are being affected more than you realize.
Another amplification is that many many parents haven't even solved this problem for themselves. How are they going to help their kids navigate social media use when they're pissing about on Instagram, and retweeting outrage garbage, etc.
