They tend to sputter when denouncing the very idea that Zimbabwe isn't just South Africa with a 14 year head start. Everything is so different!
I've finally figured out one relevant difference. The old Rhodesians had to work, hard and competently, for their wealth. They were world class farmers, and then during the embargo of 1965-1980, they built up their own industries.
So, when the new rulers of Zimbabwe started murdering the farmers, stealing their farms, and driving off the other people who knew how to do stuff, it all went to hell.
In contrast, much of South Africa's economy is mineral, which generates huge profits with small skilled workforce; the mines wealth can paper over much shortfall in other parts of the economy.