For example Poland and similar countries are amazing at the moment because of EU funding and protection.
Without the EU half of the members would be like Ukraine (rampant corruption, pollution etc etc).
In the essence the EU is net positive, despite some stupid ideas(government spying, free trade deals with south america and rushed green revolution). But still: it's very positive. Just compare Poland to Ukraine. (Ukraine was richer than Poland in 1993...)
Mass migration is real issue now and that's about it.
My 2 cents