Opera production. Since the operas themselves are not new, the productions must change.
Singing in performance. Mariah Carey falls in this category. So do Tracie Luck and Magda Olivero.
Like everyone, my biases start with what I listened to as a young person. I was in at the beginning of rock and roll, but don't recall caring. My friends hurried home to watch American Bandstand, but I didn't watch it. I was more into Broadway shows, Judy Garland and choral music.
When I first started listening to opera, it was mainly three singers: Jussi Bjoerling, Leonard Warren and Leontyne Price. These performers colored my notion of singing and still do today. The most beautiful voice ever to sing opera, from the available evidence, was Leonard Warren. He died on the stage of the Metropolitan when he was only 48 with his voice still in its prime. The beauty of his tone has never been approached, and he used it to shape incredible performances.
All three of them were singers of a certain mold: they sang directly from their musical souls. They inform my opinion of what it means to commit deeply to the music you are performing.