If I can introduce a problem domain that doesn't get a lot of play in these communities but (I think) should:

End-of-life healthcare in the US seems like a huge problem (in terms of cost, honored preferences, and quality of life for many people) that's relatively tractable for its size. The balance probably falls in favor of making things happen rather than researching technical questions, but I'm hoping it still belongs here.

There's a recent IOM report that covers the presently bleak state of affairs and potential ways forward pretty thoroughly. One major problem is that doctors don't know their patients' care preferences, resulting in a bias towards acute care over palliative care, which in turn leads to unpleasant (and expensive) final years. There are a lot of different levers in actual care practices, advanced care planning, professional education/development, insurance policies, and public education. I might start with the key findings and recommendations (PDF) and think about where to go from there. There's also Atul Gawande's recent book Being Mortal, which I've yet to read but people seem excited about. Maybe look at what organizations like MyDirectives and Goals of Care are doing.

This domain probably has a relative advantage in belief- or value-alignment for people who think widely available anti-aging is far in the future or undesirable, although I'm tempted to argue that in a world with normalized life extension, the norms surrounding end-of-life care become even more important. The problem might also be unusually salient from some utilitarian perspectives. And while I've never been sure what civilizational inadequacy means, people interested in it might be easier to sell on fixing end-of-life care.