How is she like Impa? Impa reoccurs a lot, sometimes as an old lady, while Rosalina is only in three mainline games, two of them being secrets, and only one of them being playable. SMG1 was her only major role aside from her secret playable appearance in 3D World. Mario, Luigi, Peach, Bowser, and Toad/the colored Toads are normally the only reoccurring characters aside from Bowser Jr. and the Koopalings sometimes appearing in the 2D platformers. The rest of her appearances are the sports, kart and party games; which, while yes are very important for the Mario franchise, they may as well count other spinoffs if they count those, especially Zelda with it being another of their top franchises. Heck, if Hyrule Warriors doesn’t count, I don’t see anyone going against the idea of Impa using a huge sword in Smash.
Maybe a better comparison would’ve been Daisy? She’s only in one mainline game.
I’m not complaining about Sakurai not adding more Zelda characters, I’m just tired of people trying to downplay them with these arguments that can be used for other series’ characters in similar situations, and honestly I’m tired of any argument for why a videogame character likely can’t be in a videogame crossover as if we’re all in Sakurai’s mind. I don’t think the characters are likely, either, but it’s like everyone just downplays them and tries to hammer in a potential “why” whenever they’re mentioned, a “why” that fits others already in Smash.