The EU does not benefit most Eurpean nations
Economically speaking it benefits Germany mostly. Same as the euro currency that benefits Germany and Netherlands only and hits hard countries like Italy and Spain.
Politically and ideologically speaking, it benefits "progressive" countries since the EU pushes the same neo-Marxists ideology which runs in France, Spain, Belgium, Nordic Countries etc. But only in short term. In a long term, it leads to more economic stagnation, destruction of traditional European civilization and 3rd world population swap.
For Poland, the only major advantage of joining Euro-kolkhoz was an EU single market. Poland made a trade-off: to become an EU member it has fully opened its less developed internal market for competitiona and investments from Western Europe.
It took some time to adjust to reorient and adjust the Polish economy and to take advantage of that new economic situation. That's when some of the countries, like France, started using their position to block the young competition from taking over their markets ie. restrictions on delegated workers presented by France that are again the EU rules. Basically taking away any logical reason for Central Europe to remind in this mummified institution any longer.
I see the EU as an old bitter childless lady living in a large dusty house. She is sick and freckled and developed early signs of dementia but she still has some family jewelry left which she can sell to afford a somewhat comfortable retirement and a peaceful death. That is unless her neighbor Ahmed invade her home, rob her and slice her throat before then...