So what prevents the incompetent and lazy from immigrating?

Someone immigrating is almost certainly less incompetent and lazy than the median American. Immigration requires uprooting your entire life, and it requires entrepreneurial spirit and grit. That's why many immigrant groups dramatically out-earn American-born citizens.

TBH most immigrants I've met better embody the American spirit than most Americans.

Asking basic questions about finances and job searches/security, perhaps? Do you have any original ideas or assertions to make, or do you only ask sealioning questions?