And this can be chalked down singularly to geography.
Organised civilisation started from places like the fertile crescent/Indus valley/yangtze and yellow rivers/norte chico and steadily radiated out over thousands of years as advances in technology, agriculture, medicine, architecture, and organisation trickled outwards into surrounding patchworks of tribal mini-empires, often times with these tribal empires improving or innovating themselves and their contributions trickling back as is thought to be the case with iron smelting and chariots, until they hit insurmountable geographic barriers like the ocean, or in the case of africa, the sahara desert followed by a sea of festering disease drenched jungle so nasty they were straight up uninhabitable by outsiders until the 19th century, even as they and the savannah that surrounded them harboured enough in terms of easy food production due to abundance of animal/edible plant life for a notably large population to be supported even without access to the well of knowledge and advancement in eurasia.
This is not to say that there was no contact with the outside world before the age of colonialism, as notable empires and kingdoms did spring up immediately bordering the Sahara to the south like ghana or opposite the arabian peninsular and near the nile like Ethiopia and these empires had fairly extensive and lengthy trade relations with the other powers at the time and were able to access the same well of civilizational advancement as these other states albeit at a slower rate due to the distance and difficulty of travel, but even these sub saharan empires were unable to penetrate south due to how fucking nasty the geography was both in terms of direct threats to human life and due to the strategic lack of value and desirability such areas had at the time beyond harvesting slaves for themselves and for trade.
This factor is why in antiquity, northern/western europe and non-chinese asia had an extremely similar patchwork of tribal kingdoms and nomads that sub saharan africa did, who were oft declared by ancient greek and chinese sources as the archetypical hordes of barbarians, but a thousand years later they were the some of the most advanced and dynamic regions on the planet while sub saharan africa was unchanged.
By the time of the late middle ages, western europe was already neck and neck with its direct rivals in the islamic world and its distant and indirect trade partners in china in terms of innovation and advancement, but due to a whole bunch of its own geographical super-advantages it was on the brink of a series of scientific revolutions that would turbo charge its long-term power and contributions to humanity far beyond any of its peer regions could ever hope to surpass even with thousands of years of history, and infinitely more than the as of yet effectively untouched stretches of sub saharan africa whose only real connection with the world would be the empires bordering the sahara and their association with the islamic world which in and of itself cut it off from european powers and the advancement critical mass they were about to unleash until much later.
With this context, its pretty dang easy to see why sub saharan africa was left so far behind. Its the same basic reason why civilisations in the americas lacked so many basic advantages of eurasian civilisation like the wheel and much smelting despite having their own history of technological/agricultural/whatever advancement that was extremely sophisticated in contest.
There is nothing to feel any level of shame for as this shit is entirely beyond humans of the era to have magically become aware of and even-more-magically fixed, but either blaming whitey for this or pretending they were acthchully super duper advanced but everyone else stole their technology and left them a festering jungle/savannah wasteland is just embarrasing.
Problem is, measured perspectives on history and context dont sell to loudmouthed retards looking for clout and asspats for being edgy woke.
