You have to weigh that against the fact that you are much more able to figure out how to actually do what's needed at levels where you see things firsthand. At least, that's been my experience; it's much more realistic to start a nonprofit that can make a real difference locally, then perhaps scale with time, than it is to found something with a global mission, lacking global context on how things manifest around the world.
More importantly, I'm not a utilitarian, and do not subscribe to "effective altruism" or other utilitarian philosophies. At the end of the day it's Gates' money to do with as he wishes and it's my internet account to argue against that as I wish.
Sure, but even when you apply discount rates due to uncertainty of efficacy and distance of effects, the numbers can still be big.
At this point, I spend substantially my entire life in local service (I am a schoolteacher and I give away 6 figures locally annually). I still don't think it would maximize my effective impact to ignore the rest of my country or the rest of the world.
More importantly, I'm not a utilitarian, and do not subscribe to "effective altruism" or other utilitarian philosophies. At the end of the day it's Gates' money to do with as he wishes and it's my internet account to argue against that as I wish.