The Left cannot understand colonialism because they cannot understand profit. They cannot understand that it is possible to make a profit without being exploitative.
Successful colonies must make a profit: that is, they must extract resources etc. Colonies that do not make a profit are unsustainable.
But that does not mean the poor countries lose out. Quality of life and productivity improves for the natives. Under colonialism, more wealth is created than would be otherwise. More wealth remains even after the colonial profit has been taken.
It is right for developed countries with spare capital should lend it to poor countries. That way poor countries can develop faster.