What happens to the culture of a country when you systematically import immigrants into a country, illegally or not, who don't conform to the values of said country?
Just recently -- Syrian refugee goes on mass stabbing attack targeting children and women:
https://news.sky.com/story/syrian-refugee-who-stabbed-british-child-and-five-others-in-annecy-knife-attack-was-denied-asylum-in-france-12899146Turns out many of these Syrian refugees don't adapt to westernized culture very well.
The crime increases, and more cultural fragmentation within society leads to weaker social capital and structure. Sure, if you want cheap labor just bring in cheap workers from other countries. But there are long term impacts that go beyond the economic benefits. Culture can be lost in less than a generation -- a country is not a country without closed borders.
When these refugees entered Europe many of them were already radicalized and some were also radicalized in European nations they just can't stand or tolerate Western culture. It was disheartening to see a fully grown up sane man stabbing children. What did that innocent child do to you? Children that are peaceful and open-minded are the ones he wants to kill. Some people say it is because of religion and I tell them that it is not totally the truth because the Islam I know is a peaceful religion. It doesn't promote violence and the killing of innocent people.
There are still many Syrians living peacefully and productively in Europe. Some of them have integrated so much socially, some own good businesses and work in reputable organizations. So you cannot shut your borders because you might also shut out the productive human resources. There will always be changes or alterations of cultural heritage, there are some cultures that have disappeared. Like in Africa, many cultures have been diluted with the European lifestyle, my local language is been replaced with French and English words.