Most of the things you point out about the Champs designs are perfectly true. The problem is that they're also not what the OP is talking about.
Yes, Ahri looks more-or-less like Ahri, and her movements are good, and the Spirit Rush looked cool.
Leona did indeed make that tree her bitch.
Kat is certainly an assassin and had some good expressions.
And Zyra is a plant.
But those are not the problems. It's not a question of accuracy; they are all quite recognizable. But compare Ahri's splash, i.e. that little thumbnail you posted, or any of her other skin arts, with how she looks in the video. She looks much younger and much more cartoonish, almost super-deformed; her eyes look like an anime parody and her limbs are little sticks. And that's not how she is in her art. The others are the same way - their bodily proportions are all deformed. And Leona looked much smaller and less imposing than any of the guys.
Hell, compare Kat here to Kat in Twist of Fate. This designs for the females in this cinematic just need some serious work.
....and please tell me you weren't serious with that last part. The women did not win the fight with their speed and agility - half of them didn't win at all, first off. Leona isn't supposed to be particularly fast or agile - she's a tank. And Ahri won the fight by remembering she could fight, rather than stand there and look scared.