To throw my two cents in I think she's respected as a vocalist and in parts of the music industry she's respected for what David said re the rap/sung collaboration but in terms of being a songwriter/producer and some sort of visionary ahead of her game kind of artist, then no I don't think she'll get recognition like that until she passes.
When I think of some songs on Daydream and most of Butterfly, and Sweetheart at least I think that if they were released today we'd still be praising her for her awesomeness because they're STILL a step above most of the crap that comes out. Even though she's won awards for her songwriting and that she mentions it in almost every interview and every press release says so either no one knows or they just conveniently forget that she writes all of her own material and that she's written 17/18 Hot 100 #1 singles, that she's the most successful female songwriter etc. I mean, she'll pass and all of a sudden it'll be like "Did you know that Mariah Carey ACTUALLY WROTE HER OWN STUFF?!?!" I'm not going to lie it does irritate me when people say she has no talent and she can't sing etc or that she contributes a word here or there to get full songwriting credit etc but I don't ponder why she's underrated... It's because of her image and the persona she's taken on. The GP and most of the media just doesn't take her seriously.