What today may be a modest economic gain from unskilled worker immigration could quickly become a huge burden when many of these jobs go away.
Lowering coordination and transactional costs are factors too.
Gig & sharing economy leading to better allocation of capital & labor, leading to less stuff & work overall, leading to less economic activity (production & consumption, as currently measured).
For example, it's looking like we're going to have fewer cars per capita. A virtuous cycle of less inventory, greater density (less land for parking and roads), more mass transit, fewer miles traveled, and so on.
Unless that paradox where cheaper makes consumption rise kicks in.
So many variables, trends and countertrends, technology colliding with policy...
It's hard to figure out what's going on, much less guess what's next.