When you have finite resources and an economy that is not driven by unskilled labor you cannot have unlimited immigration unless your stance is that new migrant

When you have finite resources and an economy that is not driven by unskilled labor you cannot have unlimited immigration unless your stance is that new migrants will be ineligible for public assistance. You risk bankrupting social programs otherwise. Mass migration also hinders assimilation. When you have a steady stream of migrants, those migrants can integrate into the local culture. When you have a massive burst as you would if you suddenly deregulated immigration, those individuals have enough non-native support as to never come under pressure to assimilate. This is not a good thing and is precisely what leads to massive nationalist backlash. All that being said, I do support generally increasing quotas while also largely uncapping skilled immigration.