A better legal program does. That’s the missing element.
The wall doesn’t control drugs or guns; so why would it control people?
There’s a lack of proof-in-action for your statement OD, and I think you know about those faults.
We had an immigration program that worked and illegal immigration fell to just a few 1,000 a year; then the Democrats and the Unions re-wrote our immigration laws, resulting in illegal immigration exploding to over a million a year again.
The lesson is clear; it’s the quality of the system that determines the outcome. You don’t see countries with good immigration systems have this problem.