If my ancestors had followed this, maybe we could have kept out the Puritans and the racists.
As for allowing immigrants, you've never actually even addressed the root issues, or rather root issue, because it comes down to self-ownership. Instead you turn to pragmatism -- the very approach you reject in favor of ideology when it comes to economics.
Pragmatism is critical as the guide to governmental action, including economic policy. But, what will work is often debatable, and economics is not the only consideration. Open borders would result more people and, in theory, a larger economy, but with catastrophic results in all other respect: crime, poverty, unemployment, the environment, schools, health care. Pragmatic economics does not ignore all the other problems.

























