Here's something for you to think about when making these silly drive over the fence remarks:
The border area consists mostly of hard to traverse terrain with only half a dozen roads or so on Russias side iirc. It's easy for us to see vehicles approaching, because the places where the could are far and few between.
The issue is just random people walking over. We have plenty of road networks to intercept on this side, as long as we know where border guards are needed.
Final note: there are only 9 border crossing stations altogether in a border spanning 1,343km.
The point of mentioning the road crossing points were that those places are reinforced, and yeah, it's silliness to attempt it there, leaving no possible places to take a truck over the border due difficulty terrain - we're talking about migrants here, not soldiers.
They aren't using vehicles, the russians provided migrants bicycles to get to the crossing points when they had the "flood our border with immigrants" operation active some months ago.
That leaves us with one large issue to cover: people traversing the foresty areas by foot, attempting to slip in undetected. That's where the fence comes in - they can obviously get over it if they bring a ladder, but as they struggle to even have proper shoes, a ladder becomes a luxury item they cannot afford. In any case, the fence is a slowing measure. The fence also contains alarm systems and surveillance, so that our border patrol can then pinpoint where they are needed ASAP.
The border patrol people themselves wanted this, and it's been working well.