Disclaimer: I have not done any research.
1. The standards of being rich changed
Africans riches were measured by number of cows, number of children, being an elder and things that mattered like those. This has changed over they years. You are rich if you can grab yourself the best land, have the most money and such other inconsequential things.
2. Urbanization (include modernity and its variations here)
Africans lived in villages. They moved when the season changed. God knows where we would be by now. Look at how bright we were to avoid summer and winter!
3. Africans food their own food, fruits grew on trees and we hunted the rest
Seriously, when i was growing up strawberries and blueberries were fruits that we just plucked on the trees as we ran and played. You just need to go to the supermarket and get shoked by the price of these fruits. We grew our food by the river streams. In short, food was in great supply! I imagine at a point my ancestors just went out and shot the animals and brought home food. Now it would be considered animal cruelty. Ahem.
4. Cars, trains, railways and all other things that require fuel
Kenya spends (let me google that) I cannot get the real figures but i believe in billions in importing oil. Money that could be used on other essentials like basic human needs, food, water, health, dignity.
I am a Christian (no stones here) but monogamy is one of the practices that has brought problems to African children. No wonder we have so many on the street because a man can only marry the only woman he wants to live with. It didn't matter in the past, he married the one with his child and he was free to marry others as well. African children were brought up by the village.
6. Land ownership
Land was communal. Now we have people who own land, huge tracts of land causing all manner of problems to the community.
And now i remember that we also had traditional medicine healers, midwives who were all dismissed.
I am tempted to see in the face of modernity what we can do to solve our problems in the traditional way. Again no research will be done.