She is a superb vocalist. She gets plenty of praise, but there are still people in this world who think of her as a screaming ass wiggler and nothing more.
Not necessarily underappreciated, but I think people to tend to look past her voice sometimes because they are so entertained by her performance skills.
Some years ago I'd say she was overrated because she would be a mess at times and people would still praise her for high heavens but now I think she deserves the praise she gets, she has become a flawless singer. I can see why many people think her tone is annoying tho
She has an amazing technique, but her voice really itself isn't that. To me, she's proof that anybody with a decent tone and Ok range can be an amazing singer with tons of practice + training.
She has a great vocal technique I don't she's underapreciated or overrated, since except some hater, she always has the credit for her vocals skills... I do get why people don't like her voice.