I've tried describing how it's the me-of-the-present who's caring about which sort of future comes to pass, but I haven't been able to do so in a way that doesn't fall flat. Might you have any thoughts on how to better frame this idea?

Who are the people you have been talking to? Have you considered talking to people who are more intelligent or better educated? Sometimes you just need to give up on people who can't understand sufficiently rudimentary concepts.