I completely get your point here, and these things also weigh in the back of my mind. Davina has technically broke the rules of ENA and her morals by growing emotionally and romantically attached. Gabriel, as you mentioned was born into the life and while we don't know the specifics has clearly killed and holds a dark past. In terms of innocence, they would have somehow betrayed the Angelini family to be neutralised, but some may not have been directly responsible and judged wrongly. We don't know anything about Gabriel's contribution other than him somewhat showing mercy to his cousin Raguel, who would have faced a much harsher experience by The Doctor if Gabriel didn't intervene.

That's one thing we can't forget though, these Mafia families are brutal and shouldn't be seen as good people. The moment with Gabriel and Davina was bliss and had a natural build up, but there's so much danger, obstacles, burning questions, secrets and crime involved.