The point is Sakurai is clearly a fan of his creation
And that's
exactly why she's not getting in. Well that, and the fact Kid Icarus is not an active franchise now.
It took until Brawl to get either Dedede or Meta Knight, and
that had to do with Sakurai prioritizing other characters over his own.
Smash 4 had the introduction of Palutena, who wasn't "created" by him, but was basically completely remade by him through Brawl and especially Uprising, as well as Dark Pit, who he
did create. With their inclusions having to do with Uprising being pretty much one of
the most relevant releases when he started work on Smash 4.
Uprising doesn't have that luxury now. Adding someone like Viridi now would only serve as a self-serving bias on his part for one of his own creations. Especially when it means for said less-than-relevant creation to be included that someone who is more relevant past Smash 4 from a different series had to be overlooked.
And while people often want to whine and moan about how characters get in through "Sakurai bias", that's not really a valid reason for a character.