If Africa had not been colonised, I wonder where we would be today!!! Yet, given the globalised nature of the planet, I do not even see how that issue arises: today one can talk of neutral states, but in those days, a territory either colonised or was colonised on encounter.
Technological advancement defines what is 'better off', i.e. where people want to go... and colonisation set us off towards that better-off. But that 'better-off' is a dynamic situation, and tenure among the 'best-off' - whatever the globally accepted measure, this is a game of musical chairs with tenure changing with changes in various situations. This dynamism also applies among the developing countries which belong to the lower echelons of the better-off ladder, aspiring to haul themselves up it. So colonialism was a necessary evil...
While some of our founding fathers (sic) appreciated in the evil in - averse effects of - colonialism, they were up against those leaders who did not see that evil, and the mighty, white-washing force of neo-colonialism. Africa missed an opportunity to unite in the late 1950s and early 1960s. The colonialists and ex-colonialists divided and ruled: they convinced most individual African 'nationalists' that their best interests lay in going it alone. Contemporary pleas for African unity are mere nostalgic romanticism: corporate forces are more powerful that those of political idealism. That is the greatest adversity inherited from colonialism.