Earning to give is a way the wealthy ease their conscience (not unlike carbon offsets). It is not good advice to give people with the heart, courage, and strength to be one of those front line warriors at a non-profit or in social work and to claim otherwise is garbage.
Nobody makes a bigger difference to the children and families who experience birth defects or childhood illness than the nurse in the children's hospital. Certainly not the rich goon who contributed the most money and got it named after him/her. Without that rich goon, a need would still be fulfilled by people whose lives were effected by the lack of such a facility coming together and pooling their resources to make it happen (the whole point of government, taxes, and society in the first place).
Without that nurse, there's nobody to take care of those children post surgery and offer the love, support, and attentive care that only someone with that kind of courage and compassion can provide.
No one says your mind and talents must be constrained to your job forever, but if you can do it you should.
Superman DID run vaccines to people in ADDITION to saving the world from more petty (and also much more catastrophic) crime. So the example (which in the comic is hilarious and presented ironically) the article sets itself on is a false choice.