You know as much as I love Palutena as a character in Smash and KI Uprising, I do have to admit that objectively speaking she's kinda one of the weirder picks on the roster lol.
FTR it's not really herself that's weird, she IS the most important character in the series besides Pit and its even named after her in Japan ("Light Mythology: Palutena's Mirror")...but I guess it's just because Kid Icarus itself is such a super minor franchise, so ignoring the Sakurai connection, it just seems weird to give it another fully unique newcomer when the likes of Wario, Pikmin, F-Zero, Punch-Out!!, etc all still only have one rep each. Hell, even series like Star Fox and Mother only really have additional characters outside of Fox and Ness, just because said additional fighters are so heavily based on their movesets, whereas Palutena is obviously a full blown effort.
I think if Kid Icarus was at least on the level of Metroid, as in a long running and highly influential series with tons of critically acclaimed games under its belt, Palutena's inclusion would be much more justified outside of "uh Sakurai directed Kid Icarus Uprising lol". As it currently stands, it's just three games across like 36 years, and only two of those games even got a proper worldwide release when they came out. Still love her being in Smash though!