I think you should get help.
I was depressed during my high school years and on into my twenties. I was floundering - doing poorly at university when I should have been doing much better, based on my high school results.
I did get help, and gradually improved to the point where I could have a career, do further study, get married and have children, etc (and I am a late diagnosed Aspie).
I still have up and down emotions (anxiety, anger, occasional minor depression) but I am not floundering as I was in my teens and twenties.
I don't think your depression is really the result of all the problems in the world. If you have severe depression, it is likely to be caused by differences in brain chemistry (perhaps genetic), rather than by external circumstances (e.g. the world's problems). As for depression being appropriate, you can probably make a bigger impact on the world's problems if you are not depressed. So getting yourself treated might be your first step towards doing something about the world's problems.
You can be happier than you are now, but sheer will power probably won't get you there. It would be worth getting help.