For me, the answer is that, ultimately, everyone is responsible for the plight of anyone else. Society, run by The State — an entity whose powers including being able to raise revenue, make decisions, and then spend it to fix things. Demand more from the state (and every citizen who can vote — Society and State go hand in hand) if you haven’t given up hope that we can do better.
Another alternative is we end up with Chan/Zuckerberg deciding who gets a hospital and who does not, Mackenzie Scott deciding which cities get schools and which do not, and Bill and Melinda Gates deciding which countries get more nurses and which do not.