If you start from the bottom, it's easy to grow fast when you have others to copy and learn from. It's similar with startups and enterprises. The startup always appears sleek, fast, agile, sexy, but the slow enterprise, still moves much more in a short timeframe than the startup in their whole lifetime. It's the simple difference between relative and absolute numbers, and the caps of growth.
Moldova and Ukraine were economically comparable to Poland in 1990 per capita. They have fallen far, far behind it.
Always compare comparable countries (or startups for that purpose). It is easy to explain away successes as long as failures in very similar conditions are ignored.
