"fix" Africa? Africa cannot fix itself so what you want to do? Ring-fence it and them get on with it? Same for medieval Afghanistan?
Just wondering where you get the idea that Africa is somehow incapable of "fixing" itself. Yes, few African countries look much like Western Europe or the U.S. - guess what, 40 years ago, neither Western Europe or the U.S. looked much like they do now either. Minority rights were hardly secure, unless it was the right to occupy second-class status enforced by both law and enthusiastic violence by the majority.

A common failing of the present is to assume that the current state of affairs somehow represents the natural static order of things. Afghanistan is in chaotic violence now (well, parts of the south and east, but that's all that gets reported in the West so it must be so, right?), so it must have always been in chaotic violence! East Asia is peaceful and prosperous, so it must have always been so, no? Africa is poor and afflicted with poor governance - surely it must have always been that way. Of course 40 years ago East Asia was consumed in mass violence, starvation, war, and terror while Africa experienced a generally peaceful transition to self-rule. Who knows what the next 40 years will bring? I do know this - it's probably not going to look much like the present.