So... I even agree with you that this is true, because exporting cheap raw materials and then buying back a more expensive processed product ends up creating an infinite imbalance and perpetual external dependence... This isn't a problem exclusive to Africa; you find this on several other continents.
But, my friend, I think the problem is much worse than that... it's not just the lack of industrialization, but also the precarious infrastructure, political instability and corruption within a country, the difficulty in obtaining funding for research and development projects for modern solutions, the lack of specialized labor... in short. There are countless barriers to a country's development; it's something that lasts decades, but it needs to start in some way and be continued by future governments.
Othrwise... you can build a bunch of factories in Africa, and they'll still remain trapped in a model of dependence, going bankrupt or being acquired by foreign companies.
Processing raw material is really difficult though if there's no big capital to get started with, that's why many countries are working with big company to extract their raw material and split the profit.
In fact it requires so much resource to get started, let alone the corruption that can happen and make the plan fails.
This is why rarely countries can replicate china in their infrastructure and the reason why so many of western company still stuck manufacturing their stuff in china.