Immigration - About What?

This just seems too obvious, only a politician could miss these salient facts.

"Our present-day policy objectives are different. We have a populous, highly developed nation. With a declining birth rate and an aging workforce, we need young workers for a sophisticated economy and to support a growing population of retirees and our expensive retirement benefits programs. If that is our critical need, then meeting it should be the primary goal of our immigration system.

"That is exactly what Canada and Australia do. Under their merit-based “point systems,” they score applicants for admission on multiple criteria, with the most points awarded to 20-somethings, who are at the beginning of their prime work years. They accept virtually no one age 50 or older — no one with more retirement years than work years ahead of them."

http://thehill.com/opinion/immigration/374031-a-merit-based-future-beats-our-19th-century-immigration-system

This isn't what I want, I'd like to see an almost open border policy, say yes to anyone not a criminal, but also not give out social benefits like the coffers are full. But since nothing that radical will happen, here's a rationale that at least makes sense.