By that kind of logic, I’m actually a Boltzmann brain floating alone in an infinite void, so I don’t have to worry about anyone but myself.

You can certainly rationalize anything, but I fail to see what help that is to us.

"The great subverter of Pyrrhonism [radical skepticism] is action, and employment, and the occupations of common life. [...] I dine, I play a game of back-gammon, I converse, and am merry with my friends; and when after three or four hour's amusement, I wou'd return to these speculations, they appear so cold, and strain'd, and ridiculous, that I cannot find in my heart to enter into them any farther."

Hume

> Wouldn't you want that version of yourself to live a great life?

The biggest positive change you can make, even for future generations, is to uplevel the people who are alive today.

Sure! It's just not actually reasonably possible to predict what will lead to that outcome, whereas I can sorta (badly) predict what will make me happy tomorrow, my wife happy next week, and what will best improve conditions for my current fellow citizens of the world.