Quote from the conclusion of one of the studies mentioned here: https://miwi-institut.de/archives/2028#:~:text=The%20researc....
I can only speak for my own region in western Europe (Benelux / Germany / France), for us mass immigration especially from non-EU countries has a very high financial and social cost. So high that both in Belgium and the Netherlands there is a large majority to be found in favor of drastically reducing immigration, recent polls show. However in almost all west European countries you've got governments doing the exact opposite of the people's will. In my own country, Belgium, we've got a very generous social security system and as such we attract a lot of immigration that is not interested in working (and/or simply very low skilled, often illiterate).
Among non-EU origins we're at 44.5 % inactivity, not studying nor working, (!!!!!) which is the worst score in all of Europe. Belgium itself is of course partially to blame because our social security system is too flexible, too generous and does not push to work.
Mass immigration from strongly divergent cultures is damaging western society, causing higher poverty, more crime, and rampant feelings of alienation, tearing at the fabric of social values and cohesion. Look at Germany, France, Belgium, the Netherlands, Sweden... Go for a stroll in Brussels or Frankfurt, have a look at the numerous ghettos there. Mass immigration is a lose-lose thing, both for the host country and for the newcomers who often sign up for a life in abject poverty.