Homeschooling might have some clear advantages and especially in a case when public education might pose a real danger to a child's wellbeing it might as well be the best choice, but still, I don't think generally speaking and especially worldwide, homeschooling is the way to go.
First of all, if there is a problem with education in a particular country like you're saying about South Africa, homeschooling is not a way to solve the real problem as homeschooling is usually not a viable option for the majority of the population. Homeschooling in this case can be a bandage over the problem, but not something that would cure it. After all, most of the future mothers of the country are going to come from the public school system and if it's failing then the Mandela quote actually paints a bad picture even with homeschooling rising in popularity.
That's my main problem with people advocating for homeschooling - it's not really accessible for most. If both parents work full time, homeschooling is rarely an option, so looking at education globally, it solves very little as too few people could ever take advantage of it for it to truly matter.
The next problem I have with homeschooling is that homeschooling is only as good as the education of the parent in question and in some cases, that's a problem. You see a lot of religious fundamentalists and conspiracy nuts homeschooling their children and teaching them all kinds of false and crazy stuff. So while the standard of public education might often be low, homeschooling has the potential of dipping bellow that for some people and in those cases, it's really bad for the children. I'm not saying this happens too often, but the fact that it's happening should be kept in mind.
Additionally, I think going to school usually has some non-academic benefits as regularly socializing with peers and having some independence from your parents which are also important life lessons that are more difficult to address while being homeschooled.
Still, keep in mind that while I'm talking about some of the downsides of homeschooling I see, I'm not disqualifying it's benefits or advantages, especially in certain situations.
P.S.: I hope you wouldn't mind the remark and you'd see it as constructive feedback, but I did not enjoy reading a large chunk of text that was all bold.