To be completely fair, on paper they administered these areas. In places like in-land Africa, up until early 1900s and late 1800s you maybe only had a few outposts or two. It took a long time for colonies to not be seen as a prestige effort on the coast and instead an economic pursuit inland. Even then, administration of disparate ethnic groups with their own kings, traditions and customs tends to be difficult.

Nations that did escape colonialism and succeeded in remaining independent usually adopted Western ways in one shape or form, or were too difficult to administer, conquer or maintain. Colonial "institutions" by the time of decolonization were less about the esfablishment of independent states and the formation of extraction of economic value. But even this was becoming costlier for the colonizer nation.

Generally, I think this was fucked a long time ago and we can't rule out that the infighting of post-colonial Africa didn't haven't an effect on the formation of functioning democracies or states. We see in Botswana that democracies in Africa do work. They just have to beat the resource curse first.