First of all, does this motivate you to contribute to society/mankind?
Medical field, but I am a EE, currently forced to work in defence - a field I hate, but I don't have a choice to work there, because I am on a work visa, escaping from a country at war.
Excellent, if it does then don't even worry about others. I don't
Just keep doing your thing. If it doesn't, then consider this - what is society or mankind? It is a collection of living things that depends on its environment to survive. You might not be able to cure cancer but you can contribute to the things around you.
You can enrich the lives of friends,
I'm trying, it's hard to be always positive on the outside, but it can't be helped.
I owe a lot of money to my mother and I'm the poorest and the youngest of three now adult children, everyone keeps nagging me about how I am not successful and I need to contribute equally to her well being - which is 200 euro per month, 9 percent of my monthly salary before tax, or 3 percent of my sister's salary before taxs, or 1 percent of my brother's salary before tax.
I have none.
You can raise the next generation with, hopefully, a more positive outlook and the drive to make an even bigger difference than you did.
What to do if I hate my sister's children, because her ex husband was an asshole to me and they have inherited his asshole character, have no respect for our side of the family. I can't bear being with them, but I don't have enough money to move out just yet. What to do?
You can participate in your community and help charities and make as much of a contribution as you can.
I send some money every year to some people I know in Northern Africa, completely ethnically and culturally unrelated to me, just good people going for a good project in social and public infrastructure for villages.
That way you're not just a slacker and a piece of trash.
I don't know about that. I don't feel that it's great.
You are right on point 2.
Further, if your net existence is zero - that is to say you will die in the end regardless - then the very fact that you are alive is a huge opportunity and gift to do things, to dream and chase dreams, to love, to influence, and to live.
I'm afraid I will get shifted doing things I hate for the people I despise. I got some comeuppance on the people who; I feel have hurt me, from my position some years ago, but I am not sure of the outcome, as there are great many factors which will certainly go wrong.