It wouldn't be hard to have an immigration system which is biased toward useful vs. not useful. The question is: where do you want to have the cutoff?
I'm in favor of a solid border control regime (i.e. "build the wall"), combined with a transparent and straightforward points-based system for mainly immigrant visas. I'd eliminate the inherent racism in the current system (penalizing India and China vs. Equatorial Guinea and Monaco). As a first pass, just copy the Canadian or New Zealand systems.
Where we set the threshold for entry is a worthwhile debate. Should it be anyone who isn't likely to be strongly negative? Anyone where net benefit exceeds cost? Where net benefit is >3x the annual median income?
A baseline of "not a felon, terrorist, etc." for visitors, a solid system of constraining visitors to defined periods of time (thus making it easier to grant visit visas), and a straightforward path to immigration and citizenship for high-value immigrants is a better starting point than the current immigration system.