Europe was much the same way for much of its history, but it rose to prominence out of the wreckage of the Roman Empire, colonial rule if you will. I think the difference is / was that sub-Saharan Africa had a relative abundance of food, was temperate in climate where there were few hardships from that aspect, and the different ethnic groups were sufficiently isolated from one and another to prevent frequent wars over territory, all things Europe faced.
A society that has few hardships facing it, can provide food in sufficient quantity to its people, and has no serious external threats generally, almost always, languishes in development. There simply is no reason for it to seek technological or social advancement. The native american population was much the same way. In N. America these same conditions existed and the various tribes had little reason to develop beyond basic agrarian and hunter-gatherer societies.
In Middle and South America, the societies that did go further did so out of necessity to provide food that couldn't be obtained from nature alone, because of continuous tribal warfare, and conflicts over territory. There is a common, if not exact, pattern here.