What usually isn't mentioned, is that we are already paying billions annually into it and it's growing year by year. After 2020 most of that will be actually our own money, just going via Belgium where some unelected dudes will decide how we should spend it. Add to that CO2 and a lot of other nonsense and it doesn't look like “huge beneficiaries” anymore.
Personally I think we would be better without it, sure it would take much more time to build decent infrastructure and several other things but they would be based on much more solid foundation.
But you are right that Poland or “Eastern Europe” in general is in different position than the UK and we surely won't see PolExit anytime soon. The approach of a current “far right” government is that we should try to change it from inside and that's good in my opinion.
It's not that EU is a bad concept by default, most of member states have population below 10 million people, this continent needs some sort of integration, the problem is that EU (just like many other initially good ideas) was taken over by far left, eco crazies, multi cultists, “Eurocrats” and other nutjobs, add to that Gerries who drive forward “further integration” because that means more influence for Germany, and the whole thing doesn't look good. However I'm not too exited about Brexit as without UK, the whole idea of changing it from inside will become much more difficult.
Of course friendly relations,trade and cooperation among and between the nations of Europe (except,perhaps,those still in the Soviet orbit) is beneficial if not essential.But from this side of the Atlantic the EU of today looks to be something much different...much more sinister...much more likely to have been designed to benefit a few bloated bureaucrats than the 500 million people in the EU.