Yes, and being a part of communist block we have witnessed and suffered from things people of the West have never heard of and can't see the analogies. So no, we have not forgotten anything, we're drawing conclusions, something the West seems incapable of at the moment.
Yes of course, I'd be deluded to claim that we haven't profitted from entering EU, it's the course that EU's taken that's pretty worrying for the most at the moment and rightfully so. There's absolutely no control over the immigration crisis (people here seem to be talking about all the crisis GB will witness as a consequence of Brexit, just to forget that EU has suffered as many crises, Greece, Spain, Italy, Slovakia suffering from entering monetary union, immigration crisis to name a few) and it is a concern for countries that are ethnically homogenous. But it's not the biggest scare though, just one of many. Merkel & co. threatening countries like Poland with hefty fines for not accepting immigrants at drop of the hat doesn't really help anybody, does it? There is a not unfounded fear that we're losing any sense of autonomy for which we have fought over the years with communists.
Most people here do recognise that an utopian reality where you only profit from being a part of organisation, such as EU, without giving anything back (this line of thinking is visible in posts like one by Revan I quoted above) is absolute bollocks. At the moment there's a strong German lobby in Poland which has strong influence on i.a. Polish media (yes yes, conspiracies) which is mildly annoying to say the least, nevermind idiotic European laws such as power of bulbs that cannot be at 100 Wat (Christ, I hope the nomenclature I'm using is right) hence Polish factories had to start creating 99 Wat bulbs, etc.
Then you've got plenty of restraints concerning i.a. agriculture that annoys the feck out of our farmers. You can't grow this, you can't grow that, it's simple, little things that may be perceived as vain by the big boys but in the end, as shown in GB, it's the people who vote and decide what annoys them. Then you've got people like Tusk who are responsible for destroying our country who flee to be at the helm of EU which screams problems. Overall, it's a pretty long topic that can be elaborated and argued for hours I believe.