Joel Grey has never been categorized or trained as a dancer. He is and was a musical theater actor and singer, who did some dancing when the role required it. His father was Mickey Katz, muscian and comedian, who was a member of the Spike Jones band.
Jennifer, also not a dancer, worked for months with Patrick Swaze to learn what she needed to learn for Dirty Dancing. Her dancing was never even near the quality of the female professionals in the film. Even during her finale dance with Patrick, she stood on the stage, swinging her skirt, while he did the solo, until it was time for her to make the leap.
Mya, from a couple of seasons ago, was a trained and professional dancer, cast by Bob Fosse, for Chicago. Apples and oranges here.