The USSR could increase literacy to 100%, but nothing it could do would ever make it so that IQs between ethnic Germans and Russians and Tatars were par with each other. Maybe this is why leftists like mass migration so much? It looks like Germany and the US are currently on par with Russia's IQ, presumably as a result of mass migration. Mass migration is the solution that finally achieves what Communism never could: equality between the First and Third world.
I think the correct position would have been for Russia to modernize into a nationalist state. At the very least, Communism would probably been more successful in its goals had it openly presented itself as what it actually is: an alliance of underachieving ethnic groups in conflict with First World nations. This is more or less what modern Russia is and the idea behind 'Third Worldism' and the 'Global South'. No reason to waste 50-70 years on mass killings of their own population and severe government mismanagement of the economy, Russia and China could have skipped that stage and immediately arrived at what they are now, geopolitical leaders of the Third World with functioning liberal economies. This is probably what would have happened if Lenin hadn't stolen power from the SRs. Ultimately, Russians and Chinese are high IQ peoples who would be better off without shackling themselves to either the 'international proletariat' or the 'Third World' but if that's what they want it would be more effective than rigid economic Marxism.
That communism retards economic growth is pretty well established. Note that I said it retards growth, not that it leads to economic decline. Compare Finland to the USSR, West Germany to East Germany, Taiwan to China, South Korea to North Korea, or Thailand to SE Asian communist states like Vietnam and Laos. I've never seen a convincing argument that any of these places would have been better off under communism.