the "mistake" that democrats tend to make (and it's disingenuous to call it a mistake. they generally know what they're doing.) is to take these studies that are about skilled immigrants and apply them to unskilled immigrants. so, you'll see them argue that farm workers create multiplier effects, when all of the actual data suggests that they don't. or, they'll argue that refugees are a net benefit on the social system, by citing studies about skilled immigrants.
i'm happy to bring in refugees, if we're willing to fund the social infrastructure - housing, language training, cultural adjustment classes, etc. but, the argument from our leaders in recent decades has been that we don't need to do that because "the market" will take care of it, and that is really the crux of my dissent.
the market will not take care of it; if you saturate population levels at the lowest levels of society without funding the systems required to deal with it, you just put enormous strain on the system, and everybody suffers from it. the likelihood of anybody succeeding in this mess, domestic or foreign born, is exceedingly low. what people call "the american dream" was at best a delusional fantasy in the 20th century that was propped up to advance statist interests - it's not even a desirable fairy tale in the 21st century. the entire concept should just be flushed down the toilet as utter nonsense.
they did nutritional tests on the huddled masses on staten island back in the middle of the twentieth century and found that italian immigrants had shrunk in size due to malnutrition. they were better off in sicily. but, that wasn't the point - american businesses were looking for cheap labour, so they brought them in with fraudulent appeals to a false utopia that almost nobody actually got to. what we got instead was widespread organized crime.
i don't see any use in being foolish about this, given the hindsight of history - your chances of success on this continent if you don't have an education are approaching zero. yes, there's an epsilon, but that epsilon itself is reduced by the number of people competing for sparse resources. people arguing otherwise are either dishonest or stupid.
but, the bourgeoisie is of course famously short-sighted.
it's a shame that it's not critical mass, isn't it?