And even this punts on perceptive utility, the kind that Nozick warns us about[1]: it's entirely possible that Johnny in Country X gets more utility out of $100 in charitable giving than 50 others in Country Y. But this seems like a really bad logical consequence, the kind that the Internet Rationalist EA community uses to justify spending money on AGI research instead of donating to AMF.
Overall, it's much easier to live in a world where we can determine that some set of charities are worth giving to, and not try too hard to order between them.