It's genuinely a massive problem that the median voter both 1) believes "criminal illegal immigrants" to be an astronomically more serious threat than they actually are, and 2) believes that the legal immigration process is substantially easier than it actually is.
I understand your position, but those are different situations. People straight up both envision a system much milder than exists and cannot imagine a modern world without that imaginary system. By default they have no real grasp of reality on the matter, but are usu. sympathetic to individuals.