I was asked to take on an airman on to my sqn who had been in MTC for a month ... he'd been mixing with the wrong crowd, so he said. In his words, "Seeing people shaving their blankets to get something to smoke was a real wake-up call'. He was nervous at first, tiptoeing on broken glass. He became one of my best SACs, and when I left he got a High Recc for promotion. Indeed, we exchanged emails only a year or so ago!
So ... yes, people can turn their lives around. But it's the starting point that, IMO of course, shades the issue. None of these things are simple.
Referring one of my JOs to the Stn Cdr for Court Martial for bonking a brother officer's wife wasn't a pleasant experience, but straightforward. Nor was it pleasant when I had to start the process to Admin Discharge one of my airmen, but he was utterly useless in every respect. ISTR I had to dob an SNCO heavily as well, although my memory fades on the detail. All in one Tour.
If we don't have fundamental standards, that we are all expected to adhere to, where are we?