My own desire to "make the world a better place" is rather attenuated, rather local, generally restricted to people I know and like.

In my own case, I have concluded that human morality is purely inherited sentiment. So I do stuff that feels good to me and skip the rest. So I gave $5 and a hamburger to a homeless guy I saw at a fast food place I frequent, but feel no particular desire to identify a charity which is effective at feeding other homeless people. The guy I supported made it to a position in front of my face, which is all I need to get sentimental.

I love my family and my children and my friends. I'll help them with stuff in interesting ways. If you want my help, figure out how to become my friend. Don't try to convince me abstractly that you "deserve" it or that helping you is more "effective" then helping my already fairly well off family and friends.

So yeah, I think it is quite possible to be rational in the sense of wanting to figure out truth from falsehood, and to not be particularly altruistic in an abstract sense.