The problem is that the entire world is already divided up between the imperialist powers. Rising capitalist powers cannot simply take their imperialist share, because there’s nowhere to gobble up. This causes conflict between imperialist powers, like the schism rising between the US as the world’s imperial hegemon and core imperialist countries like the UK, France, and Germany. The important bit is that Russia is playing a progressive role against imperialism.

The definition of imperialism is not arbitrary, it describes a system that results in immense plunder and underdevelopment of the global south. The west has its riches off the backs of the global south, to this day. Russia does not. If Russia was to join NATO, join the EU, transition to a more imperialist economy, etc then it would go from playing a progressive role against imperialism to playing an actively imperialist role.

Imperialism is not arbitrary. It’s the largest global obstacle to human progress, and the advance of socialism.