I honestly still don't see you making a point here. Nintendo could come up with a moveset for any of their characters no matter who they are. The difference here is that they're adding a boring character just for the sake of representing the Galaxy games.
If movesets were all that matters, then all characters should be nothing but visible bounding boxes that play differently. Video games are more than that, and Rosalina is just a boring character.
Mario and Peach are more boring characters than Rosalina.