Idk about you but I can't think of many former soviet block countries that have a healthy distribution of wealth between working, middle, and upper classes. Furthermore the list of countries given there are not places where you want to be poor.

I don't disagree. These countries often have systemic issues that go deeper than any one tax system can resolve.

Are you saying that flat tax is good, but that all countries that have implemented it coincidentally have other economic issues that are wholly unrelated?

What is the list of countries where one would want to be poor?

Obviously there isn't a list where you'd want to be poor , but I'd definetly rather be poor living in Sweden than poor living in Russia.

ex-Soviet countries like Romania and Poland are definitely on their away up.

Compare them to slowly declining western European countries like Italy and Spain.

Romania and Poland were never soviets. Communist, yes. Behind the Iron Curtain, yes. Members of the Warsaw Pact, yes (Poland is kind of obvious on this). But never soviets.