Working class people in Poland and Estonia were given the means of production and yet never overcame the anti-Russian racism despite 5 decades without a local owning class creating such propaganda.

And yet Estonia was made part of the USSR. Should it not have been? Should the Soviets not sought to unionize more countries like the one you're using as an example of a country with a racist and reactionary working class? Should any country that doesn't have a sufficient amount of the populous amenable to socialism be "isolate[d] and sanction[ed] said countries the way Cuba has been"? Which brings up another question, what is enough support, where do you draw the line as to how much of the population and by what metric is enough to warrant struggling to expand the revolution there rather than leaving their working class to keep suffering?

you can at best support preexisting movements, but you need a regional vanguard party for this to happen

In a world dominated by socialism, it is ridiculous to think no such parties would exist in every country, and where they don't, it would not be from a lack of trying, but from their immediate destruction by their state (as what happens in the US, most famously with the Black Panthers).

The comment you were responding to was "Seems like a socialist world would not let millions of people suffer like that" and it is absolutely true. No one is saying revolution will "happen spontaneously and overnight," but if a world where more countries operated like Cuba does today, or in a world where the Soviet Union spread throughout MENA and Europe, it makes no sense from a Marxist, materialist perspective, that they would simply leave any countries with a more highly propagandized public to simply suffer without any kind of intervention.