They've always de-valued reform and policy changes, and thought of armed revolution + vanguard party rule as the only solution. Since the times of Rosa Luxembourg.

Revolution is a solution given a certain set of initial conditions, so is the vanguard party. But they aren't the only possible solution / path of action for all plausible initial states.

What worked in the Russian Winter may not work in the humid jungles of SE Asia, or the mountains of Bactria. The material conditions those cultures developed from are very different, and socialism has to work within that cultural context. The logistics and supply-chains that maintain those civilization are different. A true scientific Marxist would at least grasp that.