The problem is, prison contains 3 kinds of people.
The first kind, violent sociopaths who enjoy inflicting suffering, run the place. This has an extremely bad consequence on the second kind - shallow followers who are in some sense accidental or temporary offenders. They come out much worse than they went in. This is stupid and reckless social policy, and we need to stop it as soon as possible.
The third kind of prisoners are the unlucky folks who would normally get a slap on the wrist or a minor sentence, but who, through the incompetence or corruption of the lawyers who infect the process wind up in jail anyway. These guys also suffer at the hands of groups 1 and 2, and either come out unchanged or worse.
Allowing the minority of violent felons who enjoy inflicting pain to run our prisons is massively bad - a) because it’s morally wrong, and b) because it allows them to “reproduce” by converting others to their perverse value system.
The issue isn’t whether there are too many prisoners, or not enough. The issue is that the awful way prisons are run is harming society, and it’s getting rapidly worse.
My solution (briefly) is to separate group 1 prisoners from the rest. I personally think they should be killed, but isolation on an island for life with death for escape attempts would be OK with me, as long as it didn’t cost more money.