Yeah, them 70s/80s singers were built different. As someone that produced R&B vocals, I still think MJB has a great voice and could've still been a star without the other intangibles. To stay on topic, I think Puff actually underplayed her talents with his production. His shit is more for dancing and slow grind ballads... the production has to be more stripped down for the vocalist to shine. MJB was young when she got on, so I think studio habits stuck with her to the point she hit a ceiling vocally. That scratchy yelling shit she does was Puff not knowing how to teach her that control.
The song "Be Without You" is when I think Mary actually realized her voice. I remember first hearing that song and that long note at the end and thinking there's no way she hits that note 5 years before that.