Starlight is one of the most accurate and realistic redemption stories that G4 had to offer. It's true that folks don't just switch from evil to good, and when someone decides to leave behind the bad, that doesn't make the past all better. I was grateful to the show to see how Starlight struggled after so many years of being a villain. It was almost impossible for her to accept that her old town had forgiven her. And yes, she's not 'all better', as we've seen. And yes, she deserves punishment, but instead she has been granted friendship.
Folks who have been through a 12 step program, or are trying to dig themselves out of a hole they dug for themselves, folks who have wrecked relationships, see themselves in Starlight. There are plenty of ppl out there who have caused harm to the point where folks want them to get turned into a statue or dropped into a hole forever. The notion that someone can have a shot at redemption after such flawed and horrible actions, is one of the cool messages of G4.