How much responsibility do we as individuals have for solving the world’s problems?
I would argue that the minimum is the degree of our contribution to them, and the maximum is the amount of power we have to influence them. A reasonable value in this range would be our influence divided by the number of problems we can influence without creating other problems, so long as the value for each problem is more than or equal to our contribution to that problem.
What happens if we do not have the influence to overcome our personal contribution to a problem? Then we must do whatever we can, and convince more powerful people to use additional influence.
If we don’t do as much as we can to meet our minimum responsibility to solve a problem, then society has an obligation to help us, or force us, to do so. As a bare minimum, our contribution to the problem must be neutralized without causing (or adding to) other problems.