Entirely? It depends on things like how we should weigh the present vs future generations, how we should weigh rich vs poor, whether we're working under ethical constraints other than pure utility maximization. All those are ethical questions.

I'm not sure who the 'we' here are. Ethical questions are questions about what I should do. I see no reason to 'weigh' rich or poor people, or different generations.

There are political questions about what sorts of institutions should be set up, and those things might address collectives of people or whether the poor get to count for more than the rich. But while in some sense 'what political system should I prefer' is an ethical question, the relevant questions to analyze the problem of what institutions to set up are political.