I think a lot of people were pleasantly surprised after that Grammy performance of hers. If they didn't consider her a vocalist before, they certainly thought of her as one for at least that night.
I mean besides the undeniable WFL, TTT seemed to downgrade her in many people's eyes. Thats the era that should've been called Unapolagetic imo.
But with Diamonds and Stay, she is getting more recognition as an "artist" and someone who makes good music as opposed to just dance singles.
I think the fact that Diamonds, despite not being her biggest hit, yielded her highest opening sales in the US, proves that she is becoming more respected.