Hah, not even if immigration were fully stopped would your country be saved from a major cultural/racial change.
Hope you are well.
Please allow me to add one meaningful detail to this discussion.
I am not sure if you know some less famous facts from European history but living here is not only about cheap food, child benefits, shiny TVs and cars. Europe is wealthy for a reason. If an European is poor or hungry he will not just wait to die from starvation, he will kill other man to gain food, living space or anything else he needs, he will do it deliberately and in organized, efficient way. As a Pole I understand it very well, people from the West understand it as well but may not always want to realize it, immigrants may not understand it at all. Oh, and I forgot, Europeans, in hard times, tended to support only people of their own nationality(not to mention culture or race) - being perfectly aware of that is also a 'privilege' of being Polish.
Fortunately, today we have global economy, NATO and EU. Hitler's 'lebensraum' is dead now, Stalin, Lenin - they are all gone but... it is as it is as long as we have money. As long as people are not hungry and angry.
And just to finish, if I was a non-European immigrant I really would not want to live in Poland. Not because it might seem to be poor and unwelcoming but because in case of any conflict this place becomes a war zone. I had an honour to talk with couple people who survived WW II - there was sometimes difficult to be human, not to mention to be politically correct.
So I would just like to advise you as kindly as I can: do not be so arrogant, try to study some European history and draw your own conclusions because you never know what may need to be saved in the end.