The One wrote: just because we can't stop all of the people from crossing the border, doesn't mean we shouldn't make the border more secure. If we can stop even a few by making improvements, then I think it's worth it.
A lot has been done to make the border more secure in the last few years.
The reason that "the wall" has never been built across the southern border is that Republicans and Democrats alike know that there are such diminishing returns in spending more money on enforcement. Politicians talk a lot about building a virtual wall, but they don't do too much because they know it is money inefficiently spent. Obama and Congress have done about as much as they ever will.
The way to control illegal immigration is to control employment of illegal immigrants. Controlling the incentive to come here is a much more realistic than trying to control flow. That is the direction the country is heading, better identification schemes, even if "national ID card" is too broadly unpopular to enact. BTW, it is mostly the far right that opposes the national ID card, but there are many of the left and middle against it as well.