Instead of going on those volunteer trips people should just donate some money to trustworthy local grassroots, which might be not so easy to find, but that would be more helpful.
With that money professional local staff, staying longer than the few weeks the usual volunteer does, could be employed, thereby also creating jobs locally.
But of course people might not really want to help sustainably, they do it mostly for the experience, for checking some box in their CV, for some selfish feelgood kumbaya, "Look, I´m a good person, I helped some poor ophans by volunteering."