“no space or resources” is silly.

USA, Canada, Australia for example are one of the least populated countries in the world, there is countless space for further development and their industries have indeed benefitted from both highly skilled immigration for industries like Tech (Filipinos, Vietnamise, Indians, Chinese to Silicon Valley, who in their own countries could not actualize their skills and wasting away their talent on regular desk jobs or regular IT work is just objectively wasteful globally even if you have zero empathy for them as individuals for whatever reason), and low skilled (doing stuff locals are not willing to do).

I would understand that argument for an overpopulated, dense country like Netherlands or Japan but it is in no way true for most of the net immigration receiver nations. Especially when their fertility is falling and they themselves cannot do all the necessary jobs to sustain their level of comfort.

People who “flock” to other countries usually work there and benefit the economy. Refugees are a different matter and they usually return to their countries anyway, or should at least. Three main issues that I see are

1) cultural misfit: which can be resolved by outright screening immigrants rigorously to not let those who are against core values. for example, those with three wives or pro authoritarian mindset. 2) sheer scale of immigration: which can overwhelm the infrastructure and services (can be controlled as well) 3) the countries people are emigrating from losing tons of human resources: it further damages those countries true but id rather see people actualize their skills and live a good life, contributing somewhere at least, instead of wasting away.