Here's why we need a wall, not "massive security" on the border...

A wall of drones, virtual sensors or border agents could be cancelled on day 1 of a new Democratic Presidency. Also, it would require new funding every year. If we can always have a Republican President who values border security and a GOP controlled Congress, maybe it would be OK. Can you guarantee that? A significant physical wall would require funding from Congress to tear down. Even a minority GOP could likely obstruct that. Albeit, if democrats held power for a long time, they could degrade a wall by letting it fall into disrepair.

One other problem with not having a physical barrier is it allows illegal immigrants to step onto US soil before they are apprehended. Then, they can claim refugee status (say they fear for their safety in home country) and we have to give them a hearing before an immigration judge. If Democrats were in charge, this would be mostly liberal judges. Obama found a way to go around even this minor inconvenience to illegal immigrants. Instead of taking them into custody until the hearing, he had the Border Patrol issue the illegal immigrants summons and then turn the loose into the US. Of course, up to 90% failed to show up for their immigration hearing.

Nothing but a significant physical structure will work long-term. Democrats and the GOPe know this. That's why they oppose it.