I'm not trying to generalize, but most of my female friends talk about past boyfriends, dissecting why their relationships didn't work.
From "he just doesn't get me" to "we're too different" to "why did we stay together THAT long," women tend to overanalyze past relationships.
But you can certainly be decent and work out things in a systematic manner.
What's the point of dating a girl who is still not over with her past?
You can easily become villainous in the eyes of not just the friend whose ex you are dating but also in the eyes of the members of your pack.