She has different attack animations and different movement animations. Her emotes are also redone. She also has new backing and death animations.
I think the problem here is not the fact that Kayle's Legendary skin isn't so Legendary, its the fact that regular skins nowadays are getting better and better.
But you're exactly right - and that's my point. This skin is entirely outclassed by almost all other recent skin releases. The fact it has a cool looking sword and some new quotes really doesn't cut it, in my opinion.