Most (if not all) motivations for slavery, colonization and resource extraction have been economically related, but that's not to say that all economic decisions are based in racism.

Generally the answer to every problem in every other Country isn't to just ship them to your Country, that's an unsustainable model. Typically the people who migrate are either young, well educated or wealthy - which in the grand scheme of things does nothing to fix the problems in their originating Countries.