Are they being economically successful?
Poland is a developing nation that has left communism and joined the west, as well as getting plenty of development funding from the west. It should be growing fast and from 1993 to 2007 it was with
GDP per capita growth between 5-7% typically (2001-3 downturn excluded) but since then it has completely slowed down. While in
USD GDP per capita is even worse with rapid growth until 2008 that has been completely halted since then.
Polish GDP per capita in 2015 is significantly below that of 7 years prior - Poles are poorer now than they were seven years ago, not what you should expect for a developing westernising nation that has significant development funds pouring into it. Draining their best and brightest out of the nation may help short term as they send some funds back but is not productive for the nation left behind.