The border wall is just not feasible or practical. It's not like our border is just straight flat land. There are rivers, streams, mountains, and farmlands. Animals migrate over the area & building the wall would disrupt the ecosystem. Yes, border enforcement has not been effective, but only something like 4 or 6 % of the budget allocated for it has actually been approved for use. The money is there but it's not being spent. There are other ways to strengthen our security without the wall-- which I guarantee will be vandalized. If they go with this steel slat idea, it will end up as someone's artwork or smelted down and used to make something else.
There are networks of underground tunnels that would still be used to get in underneath the wall. There are still boats & planes. People will still overstay their visas, sneak in via hiding in cars & trucks, etc. The wall won't stop them if they are desperate enough.
But the whole "caravan crisis" thing is just a smokescreen and distraction. This shutdown is hurting hundreds of thousands of federal employees & now they aren't even going to get the GS increase in January (if they even get paid then). People are accusing "the libs" of caring more about illegals than about veterans-- well, there are veterans who are suffering from the shutdown. He claimed he would own the shutdown before he reneged on his agreement to sign a bipartisan budget. He lied about signing & he lied about taking responsibility. Meanwhile, his tariffs have lost us all soybean sales to China. The investigation into the Mueller investigation was completed & it was determined that it is legitimate and necessary. Pulling out of Syria is a slap in the face to our allies and a gift to Russia. Also, removing Deripaska from the Magnitsky Act sanctions is a bad move. He was put on that list for a valid reason- he's a mobster.