Communism was always corrupt from the start and exploited the struggle of the working man when in reality it punished them. The communists stole from Ukrainian farmers and murdered them based on how many acres of farmland they worked. While Poland and Baltic states got their independence Ukraine could not and was punished heavily in the interwar period which is why some Ukrainians look to people like Petilura as their national heroes because he fought for an independent Ukraine.
The 2nd Polish Republic was a beautiful thing despite the economic difficulties of a customs war Germany imposed and having to rebuild after the Russians pillaged everything on their way out. Many universities opened and literacy rates spiked. This was the core foundation of an educated Republic of Slavs the communists always seek'd to undermine and destroy and they finally got their chance when they helped the chocolate chip cookies in WW2.
Not that I disagree but you need to clarify who you refer to when you say communism? You want to say that people who worked for free on common goal rebuilding those countries, just like they did in post war Germany, are rotten? They were mostly following the ideal you know. I agree that politicians were rotten, but are you really making the claim that isn't the case in capitalism?
Communism should be nation in its entirety, working towards a common goal. In theory. I don't see how is that rotten. But that just isn't possible due to human nature, because if you remove central authority someone else, much smaller, will think it is time for him to become authority. Which is exactly what happened before Stalin started ruling with iron fist. You can't blame the system because humans are assholes in general. Capitalism is built on that very fact and all gains it makes are based on human greed.
About Slav states before 20th century, they weren't great. People in monarchy were little better than slaves. They had free will but all their possessions were first and foremost owned by the ruling class: monarch, his immediate family and rich folks close to them. Communist taken that from them and forced them to share everything with everyone (in theory) and since villagers were always piss poor they cherished that little they had and seen communism as evil. But those same communists brought them to cities, built apartments for them, they stopped being poor villagers and got a chance to make something for themselves and their children. Same things Europe is doing for muslim youth and as you can see many of them aren't exactly grateful.
The 2nd Polish Republic was a beautiful thing
Maybe, but it was extremely fragile. Kinda like EU is atm. Sadly, strong military is necessity in human societies.