Oh really? What's your plan? How do you intend on ensuring that culture is preserved while you implement this plan? Or do you believe that Western culture is superior because it has been more successful in the last 100 years (forgetting that segregation ended less than 50 years ago, if you must include the eradication of entire populations as "successes," we can call it 500 years)? Even Bill Gates will admit that his solutions are imperfect at times.
The tricky part is a sustainable solution. Sure, you can throw money at problems, but how is the solution going to last? Like you said, there is already a lot of money involved (e.g. Bill Gates) in philanthropy, yet the problems haven't been solved yet. This indicates that the solution is trickier than you think. And if there is someone smart enough to engineer a solution, I would like to think Bill Gates is very qualified for such a position.
EDIT: Mainly, if you don't account for the culture of a place, a solution will likely not be popular enough to work (HIV prevention and treatment suffers from this problem).