I'm old enough to remember internal borders with passport checks in Europe, before the wall fell and Poland was still on the other side of that. Nice to see them moving on from that.
Thanks to the EU free movement of people, I've now studied, worked and lived in four different countries. I know people all over Europe. I currently live in Germany. Germany benefits a lot from the EU. Yes it costs money. But there's trade, access to skilled labour, etc. as well. And if you look at Poland, it's what sits between Germany and Belarus & Ukraine. So, there's a strategic relevance as well. Poland doing fine is good for everyone else in the EU.