As I understand it, the current problems come from the administration's decision to end "catch and release." For decades we have released either arrestees or asylum seekers into the population. If those cases ended up with a deportation order, there was a good chance that parent and child would be separated at the time of the deportation. In addition, in the minority of cases where we did not release an arrestee or asylum seeker, the government entered into a consent decree to maintain the children of the incarcerated person in the "least restrictive" manner, also usually meaning separation from a parent or both parents. By ending catch and release (the Jeff Sessions' zero-tolerance policy) we have greatly multiplied the number of separations and almost infinitely multiplied the number of separations where there has been no finding of guilt. If I am wrong about any of that factually, I am sure someone will tell me.
Assuming I have the basic background right, there are a couple of points worth noting.
First, catch and release allowed us to largely avoid forced, no or little-notice separations, but at the cost of seeing the immigration laws were often not enforced. That was the "policy" under the past three presidents at least. The Trumpets' argument that family separation was existing law or policy and the President is just enforcing it is an intentional distortion of the truth, otherwise known as a lie. Almost universally the United States was avoiding forced separations, particularly before conviction or denial of asylum.
Second, ending catch and release is not by itself intellectually abhorrent. President Trump made the idea a centerpiece of his campaign and we elected him. When flight is an inherent part of a crime, "release" becomes more problematic. For asylum seekers, there is a great potential for abuse of the system by people who say they are seeking asylum when in reality they are just seeking a better life.
Third, the real problem in my mind is not what the administration has done, but how it has done it. If you are going to end catch and release, you build an infrastructure that allows families to be treated humanely while in custody and you get hundreds more immigration judges, support staff and appointed lawyers to move the court cases at a rate much faster than what happens now. As with the first travel ban, it seems like those in the administration just woke up one day and decided--today is the day we are going to do a 180 on established policy. Lets see what happens. And what happens is a whole bunch of awful crap.
Fourth, if a wall would fix all of this, why don't we just get on the phone and find out when those Mexican wall payments will be getting here?