Marxism used to be the dominant ideology of resistance. Why? Because Marxists often aided, and sometimes led, national liberation movements. That's the main reason -- perhaps the only reason -- for its popularity in the early to mid 20th century.
That is also the reason why Marxism never became very popular in imperial powers themselves, (now integrated into one multinational empire under US leadership), for their peoples never had to look for a powerful political tool that would serve as an effective weapon to counter colonial and neo-colonial subjection.
The political currents on the Left that prioritized local class struggles at the expense of national struggles, such as anarchism, council communism, Trotskyism, and so on, did not find comparable mass support worldwide, for their ideas did not resonate with colonial and neo-colonial subjects fighting against imperial masters.
Will things be different in the 21st century? So far, there is no sign that they will be. The most successful current of leftists in the world today, Hugo Chavez and his supporters, are anti-imperialist patriots first and foremost.
Historical materialists can make contributions to humanity to the extent that we make ourselves useful to people in the global South, religious or secular, struggling for republican democracy against US hegemony, seeking to advance the interests of working people in and through national struggle.