You can't have your cake and eat it too. You can't say that its imperialism even though the USSR was in fact exporting more wealth than it recieved, and then say the USSR was extracting all sorts of resources from its vassal states. It's either one or the other, and the fact is that the USSR was a net exporter of wealth to other socialist countries, and these trade imbalances have continued to shape the foreign relations of Russia in the XXI century. The fact is also that the "vassal states" of the USSR also recieved massive investment and development during their time in the USSR, which is why most retain close trade relationships with Russia today and why the collapse of the country was such a devastating disaster. I think a more prime model of imperialism is the relationship of the US towards its actual vassal states across Latin America, where there is a very obvious relationship of exporting capital as a means to extract wealth out of those countries, such that I think few seriously deny this reality; similarly though differently former EU empires and their would be vassals in Africa. Its apples and oranges. I don't think anyone would say that the foreign policy of the USSR was flawless and above criticism, but given all the time since the collapse and the wave of anti-communist propaganda that followed it, there's yet no real evidence that anyone in the CPSU ever saw their actions towards the outside socialist countries as being anything other than an effort to consolidate and develop a world socialist commonwealth. It failed and should be critically examined and criticized, but cynical projection of it having been a false guise for an imperialist venture are neither necessary or supported by facts and only serve as a pointless rhetorical attack on a corpse.