It sounds like you're projecting your own beliefs onto teenage girls. Even if they cared about income inequality or climate change as much as you think they do, that's still the fault of social media. It's counterproductive to be overly worried about something that is outside your control, especially when it doesn't affect you yet. Everyone is going to suffer the effects aging and death, so it's a very logical worry. However, if social media is filled with reminders of sickness and death, which is causing you anxiety, then you should quit.