My opinion on this is simple. Everyone has a voice for their writing, just like everyone has a voice for talking. The trick is to figure out how to use your voice in service to your story. It's not easy, but it's definitely doable. Imagine someone with a smoker's voice, perhaps a ratty emaciated blonde woman who's been smoking for so many years she sounds like a fork being dragged though gravel when she talks. While she could tell the story of a happy princess who finds the perfect husband after some minor travail, she would not tell that story using the same words, phrasing, gestures, tones, etc... as say...Pavarotti. She could tell any story she wanted to, but, to be most effective, she would not use the same techniques as others. She would play to her strengths and be aware of and manipulate the effect her voice has.
Rather than 'finding their voices' writers need to figure out 'how to use their voices' to best effect. And make no mistake; the same story told by the same person before and after they learn to use their voice effectively will sound very different.