What would you call the accuracy of "dependency theory" in explaining today's world?

Dependency theory can certainly be credibly applied to today's international structure and to the nature of relations between more technologically-advanced nations — the so-called "core" states — and their poorer, less-technologically-advanced partners in trade — the so-called "periphery" states. 

Dependency theory, a product of academic analyses of the relationships of the rich to the poor, dates to the 1960s and 1970s. According to this theory, international relations, at least with respect to relations between rich and poor, invariably involve what we can call "a zero-sum game." The rich states prosper at the expense of the poor states, whose natural resources and cheap labor are exploited to make the populations of rich states even richer. While the post-colonial world saw the potential for the emergence of exploited "Third World" nations to the ranks of the middle class on the basis of their wealth in natural resources, that development has simply not occurred. The reasons for this are varied, but certainly include systemic corruption and ethnic conflict in countries like Nigeria and the Democratic Republic of Congo (formerly, Zaire), as well as in other resource-rich nations like Venezuela, where mismanagement and ideological zealotry destroyed once-vibrant economies.

Do such "domestic" issues like corruption and ethnic conflict absolve the rich states of responsibility for the continued social and cultural degradation of the poor states? In some instances, the answer is yes. Decolonization was a messy business, with the departing colonial powers failing in most instances to properly prepare their now-former colonies for independence. In those cases where independence was achieved due to violent opposition to foreign occupation, this can be explained, although only in the most negative sense. After all, how easy is it to extract oneself from a losing battle while establishing stable governing institutions for the use of the soon-to-be independent nation? The fact remains that, with some exceptions, newly-independent nations were ill-prepared to run their countries, and institutions failed while corruption and incompetence became the rule. Think about that most-renowned of former colonies, Afghanistan. Withdrawal of British forces left behind a patchwork of competing tribes and clans that rarely got along with each other. Later, defeat of the Taliban-led government saw the emergence of a U.S.-supported government that has failed miserably due in no small part to tribes' and clans' frustration with the ruling Pashtuns' endemic corruption.

Anyway, the "zero-sum game" that characterizes dependency theory has not disappeared. That corruption and incompetence has worked to the advantage of the rich nations, which continue to import vast quantities of minerals and oil from poorer nations. There is still a sense of a serious imbalance in ostensibly equal relationships between countries from different ends of the economic spectrum. The infamous practice of outsourcing manufacturing, and even service-oriented, sectors has in many cases served merely to further enhance the notion of exploitation of the poor by the rich. Even China, once a colony of various European powers like Portugal and Great Britain, is now among the more avaricious exploiters of resource-rich "periphery" states. Chinese engineers, technicians and labor crews are present throughout Africa, as the Chinese government pursues business deals with poorer countries for the purpose of securing access to raw materials to sustain its enormous economy.

Yes, dependency theory is relevant today. Exploitation of the poor by the rich continues, and the situation does not seem likely to appreciably change any time soon.