South Africa was hardly a utopia under Apartheid. Yes, there absolutely was more technological innovation and better infrastructure but the society back then was just as fractured but in different ways. There was less crime in the cities but in the townships it was often just as bad as it is across much of the country now. Keep in mind it was the whites who kept importing massive amounts of black labor and shipping them out to the shittiest real estate where they had to live in tiny matchbox houses, because whites couldn't be bothered to mine their own gold while reaping the benefits of their massive welfare state. I'd say one of many causes of the demographic tensions in South Africa today stem back to the whites repeatedly shooting themselves in the foot, all to maintain what was essentially an American-style suburban fantasy land for as long as they could. It was the white Apartheid government (along with the U.S.) that turned on Ian Smith in Rhodesia, essentially causing him to fold and leading to Mugabe's takeover, thinking that the 'winds of change' wouldn't spread to South Africa.
Likewise, this doesn't mean blacks (which I hesitate to even use as a term in this case because it lacks the nuance of ethnicity) are totally incapable of civilization or running their own affairs. There are plenty of countries in sub-saharan Africa that are relatively well off - far better off than South Africa, even. Botswana of course is the first that springs to mind. It's like the Switzerland of Africa and has excellent race relations. Rwanda (these days, at least), Namibia, Zambia, Kenya, and Malawi despite their variances in wealth are all quite stable. Nigeria is a rising star that, if it's able to take care of the sectarian issues in its north, has immense economic and political potential.
During Apartheid there were still bombings, massacres and riots left and right. You had the Church Street bombing in Pretoria, the Amanzimtoti bombing in South Natal, the Sharpeville massacre, the lacing of anti-tank mines in northern Transvaal which killed a shitload of civilians, and many, many more. Mandela was absolutely a terrorist in the first half of his life, but despite his many flaws he did change in prison and disavowed his previous stances - the violence spurred on by his (ex)wife Winnie Mandela reportedly horrified him. I think he was a very flawed but wise individual who understood that in dismantling Apartheid it would be idiotic to antagonize the non-black population and basically start a civil war. Many of the more pronounced issues you see in modern-day South Africa ramped up after his death because he was a moderating force in the ANC. Without Mandela around to keep the more radical elements in check, you ended up with the more hardline leftists and corrupt types taking control.
I don't think white South Africans should flee the continent. Africa is their home and has been for centuries. I respect the grit of those who choose to stay, same for the 30-60,000 or so whites who despite everything still live in Zimbabwe and manage to eke out a living. Boers have been living in South Africa for so long that their culture is quite removed from the modern Dutchman. It would be like saying Anglo-Americans are largely indistinguishable from the British. I also think something absolutely needs to be done to put a stop to the farm murders.
Basically, what I'm saying is that Apartheid South Africa was shitty in many ways, and modern South Africa is also shitty in many - but different - ways. We shouldn't romanticize Apartheid just because much of current South Africa is a shithole. I know this is a situation where it's very easy to ignore nuance but we mustn't forget.