If we assume, like you do that Africa is lost cause what about Latin America?
For better or worse, Latin America has more or less erased its pre-Columbian history. All of the animosities of the indigenous past have disappeared down the rabbit hole of 5 centuries of forced assimilation (into Spanish or Portuguese culture) and inter-marriage between natives and African and European settlers. Latin Americans are basically either Spaniards (LA ex-Brazil) or Portuguese (Brazil) with black, Amerindian, white or racially-mixed features. For the most part, they speak Spanish or Portuguese as their sole native language, worship in Catholic Churches (although it has to be said that evangelical churches are making great strides) and are philosophically and culturally Spanish or Portuguese. This mostly limits the scope of domestic strife to differences arising from ideological disagreements or power struggles. In Africa, the struggles involve blood-and-soil and religious issues of the kind that characterized Hitler's great purge of European Jewry and Islam's murderous rampages (in antiquity) through North Africa, the Middle East, Central Asia and South Asia. Rwanda and Congo were blood-and-soil. Sudan was both blood-and-soil and religious.
I don’t assume Africa is a lost cause; the Western governments did. Africa has a lot of natural resources (gold, oil, diamonds), incredible agricultural potential, and a large number of educated people in some countries.
As young countries (many less than 60 years old), their growing pains have disillusioned people who expected a lot more from them. Time will tell, but they have large obstacles to surmount.
Latin America, though not as young, has many of the same problems, though to a smaller extent. In both cases, the countries involved have to sort out their futures themselves - foreign involvement isn’t bringing about stability without the use of anti-democratic strongmen.