As Paul Graham put it in another context:
"Why do so few founders know whether they're default alive or default dead? Mainly, I think, because they're not used to asking that."
People aren't used to thinking of civilization in these terms. We make retirement plans etc divorced from the projections of change to come. If we rationally considered priorities, you'd see much more popular support for actions designed to address the problem, such as increasing carbon taxes, cutting other taxes, and making an international framework to get other countries to do the same.
There's a scene in 12 Monkeys where the protagonist is in a mental hospital in the past, before a virus takes out the civilization. The psychologist asks if he came back to "help" them. The protagonist looks confused and says "how can I help you? You're all dead".
We have such a flurry of concern and activity aimed at the present. I can't help but have a similar feeling when I observe people making plans and not accounting for the predicted future, even if they claim to "believe" in climate change.
If people truly believed in it, you'd see much different political priorities. Right now effective action tends to be unpopular. Income taxes (taxing a good thing) have much more political support than carbon taxes (taxing a bad thing). I find the situation baffling.
More from Paul Graham's article:
"There is another reason founders don't ask themselves whether they're default alive or default dead: they assume it will be easy to raise more money. But that assumption is often false, and worse still, the more you depend on it, the falser it becomes."
We assume it will be easy to solve problems in the future, with future technology. Or that we will have surplus resources in the future, when worsening conditions cut crop yields, cut water, increase civil strife, and when the global population is larger and total emissions are higher.