"There is a genuinely selfish reason to make the world a better place"

A couple problems. For one, prosperity scales. Secondly, you can't just teach a man to fish in other places. We'd rather give them a fish for some reason, and there's still the matter of dealing with the assholes who keep killing the fishermen. Thirdly, investing in someone else's great-grandchild won't appeal to people who are having a hard enough time building a better future for their own sisters and daughters.
I could poke more holes in the argument, but in essence this is a very optimistic essay that doesn't actually take human nature or the state of the world (beyong GDP, at least) into account.

Check out their video on time if you want to feel very small in the universe indeed.

I see why there can be a certain amount of self interest in "altruism." But it also seems that the net benefit to an individual is less than the amount of energy/money/effort/whatever that any individual expends on his own. That is, you may get a hundred dollars of benefit over your life but you kicked in a hundred hours of tutoring/volunteering/helping/whatever. So there really is some selflessness in altruism, even if some benefit eventually goes to the benefactor.

Of course, if what you call "altruism" is just agitating for higher taxes on others to fund various programs that let you feel that "something is being done" about an issue that appeals to you, then that's more hypocrisy than altruism, since you want to feel better about "doing something" without having any of your own skin in the game.