They're also the 3rd smallest net recipient of EU funds per capita:
It is a tax haven, with one of the highest GDP / person in the world, why is it, by magnitudes, the biggest recipient of EU largesse / person??!
Additionally a lot of the EU's institutions are based there or have offices there, some of which might count as investments as well.
Lastly, everything there is really expensive. So you need to invest a larger amount to achieve the same thing as elsewhere.
I have been to Luxembourg and to Hungary, Bulgaria & Greece - the otherwise obvious contenders for "poorest" in the EU and Luxembourg should not be in the picture.
Another argument: Poland's GDP had already been growing at a similar pace before it joined the EU (but after it got rid of communism).
Also, the reason you've given doesn't explain why it worked so much better for Poland than for Czechia, Slovakia and a few others.
It's hard to see the other paths they could be on tho. One person's failure is another's raging success. It might be a bit like the way we take a peace for granted, because we can't internalize the cost of all the ways it could have been worse.
There are also crowds of young anti-woke Poles claiming that Poland should leave EU because we would be better without it and claiming that EU is puppet of Germany. I've also seen opinions that Israel is a puppet of Poland, aimed at Israelis. If you want to, you will see all opinions you could imagine.
But sure, sock puppets also follow the crowd. Good money in it: https://www.bbc.com/news/articles/cj38m11218xo
The "logic" of xenophobic nationalism is that narratives are selected for how well they (1) cast "us" as victims, (2) cast some convenient "others" as villains, and (3) fire up "our" feelings of hatred. Neither logic nor truth are particularly desirable - and narratives which are particularly defiant of logic and truth may be a way of virtue signaling within xenophobic national social circles.
On the contrary. Since the EU has no meaningful penalty mechanism other than withholding funds, and enormous capacity for shared damage absorption, once a country passes a certain threshold of development membership in the EU actually encourages government misbehavior including democratic backsliding, because it insulates the government from many potential adverse consequences.
For example, governments around the world have to fear violent revolution. But in the EU, the shared desire for law and order is so strong that the rest of the members are likely to support a member state in repressing such a revolution with essentially any degree of brutality, regardless of the condition of that state’s democracy, because the alternative (a successful coup in an EU member state) is impossible to contemplate.
There is no lesson of "democracy" to give. At best it is a guided democracy, and this is very generous.
For example, VPNs are going to be forbidden, and the free speech compared to the US is a little toy.
Elections are often a facade in many EU countries.
In France for example, it's always the "right" (btw you can be socially or jailed if you support them by using the wrong words) against the existing party, and communists are begging it's better to vote for the existing party, than support the newcomers.
It's a loop, this is why there is this joke that voters are "beavers", because at every elections they are asked "build a dam" against competition.
There is the same beaver thing, over and over again for 30 years.
Even people that are actually elected you have nowhere your word near their decisions (and even less near Von der Leyen and similar people).
Poland understood long time ago that it needs a safe country, and that they need to make sure that the people in their country are fine and safe before helping the whole planet.
Hungary and Poland are a little bit in the same boat, their relative independence saves them (e.g. refusing the EUR currency, refusing some policies) that allows them to have more leeway to support the local people, while benefiting of the funds from the EU and Schengen.
The EU prevents your money from being stolen, except when the EU itself decides to withhold or deduct it. Hungary has lost over a billion euros in ECJ daily fines...
If you push it even further, this is forgetting about the hundreds of billions that are centrally distributed to third-parties (and this is just Ukraine!). So, your money, our decision.
US printed so much that basically entire global economy had to pay for it in huge inflation in the years that followed. And all that freshly printed money ended up in pockets of US billionaires.
Tight global integration is not a bad thing. Even if we took at face value your argument that a strong domestic market protected Poland in that case, you can't cherry pick the one instance in which lower-than-expected integration was beneficial without also considering all the other times in which it was harmful.
You could get the money but you had to get bureaucracy to be right and transparent to cut down on fraud, and that helped the rest of the govt to have less fraud.
Furthermore, as the GP hints, EU funds earmarked for Poland don't necessarily remain in Poland as investment. Much of that money circulates back into the pockets of contributing countries. You have to look at the entire paper trail to understand where money is actually ending up.
Also worth noting: Poland didn't receive a dime of reparations after the War. Germany (and with later contribution by the Soviets) had unleashed such mind-boggling destruction on Polish cities, towns, cultural inheritance, industry, etc. that only the so-called Swedish Deluge matches or exceeds this devastation.
The EU presents certain clear economic benefits for member countries. Nobody disputes that. But the patronizing and paternalistic narrative of some countries - reminiscent of their goofy rationalizations for their occupation of that region during the 19th century - need to go away.
Poland received virtually all of the lands that were considered Prussia though.
Probably worth more than the EUR 1 trillion fantasy figure that Polish right wingers demand.
The fucking krauts (both the German/Prussian and the Austrian/Hapsburg varieties) can and should toss them a few złoty for economic development as recompense for the horrific treatment they've dealt Poland over the centuries. It would be nice if the Russians would too, but that's not the reality we currently live in.
Times were much better.