I should know, because I have experienced it myself. In Ghana set up stalls for trade on the sides of major roads, at considerable risk to their safety. Successive governments have tried to force them away for a while, only for people to denounce those actions as heartless. Invariably, they slowly creep back. Imagine those who promote this situation are fined or jailed. Is that a case of being authoritarian, or a case of robust enforcement of safety rules?
Here you have an African country enforcing the rule of law and a strong national identity, and with actual results to back it up. Of course mistakes can be made, and I'm not holding up the Rwandan regime as blameless in terms of human rights. But if you you focus on quality of life of the average citizen, they have improved a great deal.
Ghana too was doing well in the last decade, but now has taken a turn for the worse since the current government took over. I live in Ghana, and the level of corruption now, and the neglect of a proper development agenda, is unbelievable.
So, I don’t think there is necessarily anything that makes black-majority countries incapable of curbing corruption.