From the source linked:
EU membership ought to have been a boon for Poland, a country which in 2004 was still recovering from the dead years of communism. Access to Western European markets ought to have supercharged that recovery.
Initially that is what seemed to happen. Between 1992-2004 the Polish economy more than doubled in size from just under $100billion to $250billion, according to the World Bank. Between 2004 and 2008 it doubled again to peak at $500billion. But since then Polish GDP has flatlined.
Of course the global recession of 2008/09 affected all economies yet for the Polish economy to be a little smaller in 2015 than it was in 2008 is a shocking indictment of EU membership. The EU has managed to turn a high-growth economy into a stagnant one.
Why was Polish GDP flatlining? Why did millions leave Poland?
I literally send you a credible source that shows its similar to 1985 year. Are you saying that it was high during USSR occupation or ignoring the source?
Not only is the gini coefficient misleading, but it only goes back to 1985 in your source. Upon the adoption of capitalism, Poland has had unstable growth to even flatlining, is now being sold out to foreign companies, and again, has purged its left in favor of the far-right.