Consider specializing in making money and donating the money to people who specialize in $PICK_A_CAUSE_DEAR_TO_YOU, if your primary concern is about impact and not about personal fulfillment. NGOs are often not well set up to metabolize the labor of developers, and at some things which you think are helpful will be perceived by the organization as a threat (e.g. at many organizations, anything which decreases the required headcount to operate attacks a primary reason for the organization to exist).
You're also unlikely to be an expert at $PICK_A_CAUSE_WHICH_IS_DEAR_TO_YOU for the same reason you're unlikely to be an expert at heart surgery or filing business taxes. Those strike me as important enough to be done by someone who knows what they're doing; your mileage may vary with respect to causes dear to you.