you indicate that Africa must
"build more – but mostly better – human and physical capital"
The crux of the matter is that if these investments in total factor productivity result in greater economic growth, why are they not made? Government should see that doing so will raise their tax revenues, and (in the case of decent macroeconomic management), the financial sector should be able to channel resources to those investments.
The fact of such severe under-investment in human/physical capital implies either the risk of lending for these projects is overwhelmingly high (eg. due to corruption causing poor allocation of resources) or the perceptions of risk are unrealistic.
More information on why these profitable investments are not made is the real issue.