You know, I understand where you're coming from. As a teenager I dealt with a lot of depression because I realized how screwed up the world was, and how powerless I was to fix all of it.
Even now I still struggle when I see how careless a lot of people are. But you know, I've also come to realize it takes people like us to balance that out. There's a lot of awful stuff out there, but it's not all bad. We can do our best to change that, even if we only affect the people in our lives. That can still branch out and influence others to be better and treat one another better. It's idealistic, but it's also something I've seen myself.
Just don't lose hope. Look to the good in the world. Do your best to add to that. It'll help, I truly believe it will.