Well, yes, volunteering in Africa does not make sense from a cost-benefit perspective, unless you actually posses a skill that is in short supply over there (i.e. doctors). However, volunteering at your local homeless shelter, orphanage, retirement home or women's shelter, where your work does not incur any extra costs for the institution you are helping, is a completely different thing.
It depends how short-sighted your goals are. If your goal is solely "build a house in rural Angola", then yes, hire local talent. If your goals include "making our youth more worldly, exposing them to other cultures" or "extend soft power by building bridges between citizens", then it's very worthwhile.
The author of the article strikes me as a 'worth of everything and value of nothing' type person, only seeing the literal end goal.
Those goals are not strictly related to volunteering though, they can be accomplished with exchange programs or tourism (if done through local tour guides). The main issue with voluntourism is that it does not promote sustainable growth in the communities it is trying to help, and therefore is not a good long term solution for the problems it is trying to solve. Not to mention taking jobs away from local workers who could really need the money.
Not to mention taking jobs away from local workers who could really need the money.
Jobs that aren't currently being done? Is it really a stolen job if it wasn't being done?
Another problem with foreign aid is that if you don't actively manage it yourself, corruption can very easily divert it (and regularly does). At least by sending in the kids, some of it actually gets spent on the intended target. Maybe the kids made a shitty house that has to be rebuilt, but hey, at least now the bricks are in the right place... and now there's a job for that local worker you wanted.
My point is that the article has an extremely simplified view of what's going on. There's a number of interests and angles at play here, not just the 'veiled selfishness' that the author is painting of the volunteers.