Few people would suggest that not having prisons is a better alternative than having them, however unpleasant. Similarly, in a world of deinstitutionalization it seems unlikely that 500k people living on the streets is the best of all possible worlds.
If anything its an example that suggesting to bring back asylums should be considered synonymous to an advocacy where the abuse of detained people is taken into account as an acceptable cost.
But mind you: The last time we implemented detaining people, this was in border control, and resulted in the border patrol trafficking children through abusing the child separation policies at the time. There are still tens of thousands of missing children from this policy, implemented for a scant few years.