I dunno. Only Mumei can speak for Mumei, but I always got the impression that he liked some of her stuff, but was critical of the fact that she's one trick pony, vocally.
Even though, in my opinion, that one trick is one hell of a doozy.
Well, I'm critical of Florence because she's a one-trick-pony
who doesn't do her trick very well. Florence is - much like certain other singers -
loud. She doesn't have a lot of resonance, and her lack of resonance was really, really apparent in that Grammy Tribute where even non-vocalist Martina McBride was clocking Florence.
She doesn't have a very forward placement and it has a throaty quality (much like Adele, but much more pronounced), because she's producing her volume by banging her folds together as hard as she can and going all-out. She produces almost no squillo and is often slightly under the pitch, with a lot of tension in her voice and that ridiculous tremolo. But because she's loud and her name isn't Christina, she gets a pass.
Oh, and
since you wanted to bring up Bey.
Well, generally a tribute song requires a pulse to be capable of performing.
Most of Mumei's favs are ineligible.
Your faves give tribute to my faves to remind us of what we've lost.