The GDP is not growing at even close to the rate at which people are retiring. As the population ages, things will only get worse. Also that's also probably why temporary workers are all the rage, most of them will never get a citizenship but they contribute their tax dollars anyway. Which is kind of genius to be honest.

Long waitlists for a green card is a feature, not a bug. Also unpopular opinion but COVID probably helped save on a lot of future social security cash.