Putting a human face on things does seem to be terribly important to get smaller donors to donate long term.

My own mother has been donating for years to a particular charity which puts young girls in a particular country who did very well in end-of-primary school exams but live in absolute poverty through secondary school in a third world country. Donors are explicitly paired with a child and exchange letters twice a year. (donors are asked to write something or other even if it's just a postcard because it scares the girls if their donor goes silent even though the charity doesn't kick kids out if their donor dies but rather pairs them with a new donor) Donors also cannot "overfund" one individual to avoid jealousy and unequal treatment based on funder.

I doubt the scheme is the absolute best bang for your buck though it probably does pretty well if you value education highly.

It amounts to a couple of hundred euro per year but they have exceptionally good donor retention with some donors explicitly putting aside enough in their Will to put their girl through the rest of her education.

They're not sending money into a generic money-hole, they're taking care of an individual who they've talked with and who dots her 'i's with a squiggly line and draws faces in her margins in purple pencil.

Perhaps ubiquitous cheap tech will allow some big problems to be handled in such a manner as to give feedback to donors. Tell them about the million people in the refugee camp but put a ring around a half dozen families who are getting the malaria nets you funded and the vaccines you paid for.

Right now coordination in those situations is such a nightmare as to make that impossible but I could imagine cheap electronics solving communication long before solving refugee camps.