At the beginning of the game, they'll have the opportunity to pick one of three starter Pokemon divided between Water, Fire, and Grass ... Ivysaur, and Venusaur may not be the best Grass-type ...
As such, the move has very little use in Pokemon X and Y. Greninja is a Water and Dark-type. Here are the elements it is weak against: Venusaur's Pokedex picture in Pokemon Scarlet and Violet ...