You can't define it, but you know it when you see it.

People who can dance can dance. You just see it. People who can't dance can be entertaining in a clown show kind of way. See Footloose, Hitch, etc. Bad dancing is funny.

But good dancing, no matter the genre, either is or it is not.

I'm not sure there is another art form that is so completely hit or miss as being able to dance.

And that's not to say if you can't dance that you shouldn't. There is dancing for art, and there is dancing for joy. Everyone on the planet can dance for joy.

But on a stage, either you can or you can't.