This is an interesting comment, because arguably although those countries did know well what they
didn't want (Soviet domination, socialism and the one party system), it's not at all clear, from the developments in these countries, what they did want, or how they intended to achieve it:
- Poland now has an extremely illiberal system of government, without the basic republican separation of powers, secularism, or civic freedoms.
- Hungary also is run by an extremely rightwing government which dismisses most foundations of democratic republics using antisemitic conspiracies. If
- Romania is run by kleptocrats and considered borderline too corrupt to be a full member of the EU.
- Despite the GDR having been integrated very smoothly and quite generously into Western Germany, the exemplar of a stable Western European democracy, around half the voters in the former East support either pro-communist or xenophobic, pro-fascist parties.
- Lithuania fails to guarantee basic rights to minority groups.
- Bulgaria - both communism and fascism remain extremely popular.
- and so on. You also loaded your examples - the countries which did join the EU are generally quite a lot better than the ones which didn't such as Moldova, Ukraine, etc.
To be clear - I think that Poland and Polish people have an absolute right to self-determination, and it was never ok for them to be dominated by the Soviet Union, whether by soft power or by violence. However, I think it's fairly clear that if being a modern Western democracy like Denmark was what they wanted, then they failed to achieve it. They have the absolute right to be what they currently are, but they should at least be honest about it.
There's also an irony that in the 1970s and 1980s, when progressives in Poland claimed that they wanted Western-Europe style liberal democracy, the communist apologists, both in Poland and in the Soviet Union said that they were actually fighting for domination by the Catholic Church, inequality, exploitation by rich capitalist countries such as Germany, antisemitism, and so on. Well, they got rid of communism, and what did they adopt? A right-wing, institutionally antisemitic, illiberal system, socially controlled by the Church, and trapped in an economic system run by richer countries.