It does not. Illegals get by through sea, tunnels, hell even planes.
An EO, especially with a 28 person staff, doesn't not suddenly magic a wall into existence. Several thousand miles of shit that has to be approved, contracted, and built. It will take YEARS, assuming there were no hiccups.
But if you honestly believe that a wall will keep out people, especially people who go all or nothing to escape their hell hole of a life, you're in for a grim surprise.
The only way you can address immigration is by understanding its source. Why would a person leave their home and risk their life to get into a country that may only be a modicum better than their current situation? Because that situation is shit.