One of the things that those who really want to help could take on board is the need to work out exactly what is the best way they can contribute for those who need it. Money, yes, practical help, yes, but just being there and being willing does not necessarily do anything useful.
As the writer says, the skills to build, teach, diagnose and treat illness and co-ordinate work are what is needed. If the bricklaying that these girls were doing was dismantled overnight to be done properly, their "help" just caused more work.
Part of the preparation that organisations do beforehand should include finding out what will really help and train the volunteers for it, or select them for their abilities. There is a lot of goodwill there, but it needs channelling.