It was definitely during Smash 4 speculation. Seeing so many Uprising enemies, the Palutena Guidance, and 3 Kid Icsrus characters turned off people from Kid Icarus. Many Smash fans still feel that way despite us still getting Chrom (a 7th Fire Emblem character) and all veterans returning. They feel that Kid Icarus is too niche to get more than 3 characters, when it wouldn’t matter in the long run.
Well, a playable character is something big (even an echo) but being niche doesn't stop Earthbound from every previous content back (stages, items, AT) meaning that we have all the magicant things in HD, the return of the Chimera, we have a new item and more importantly, it still got FOUR new characters appearing during the Final Smashes! Appearances of Paula, Poo, Kumatora and Boney is something big.
And that's great! I'm not complaining at all.
But with that (and Chrom), why would a Kid Icarus character be problematic? Because it's Sakurai's game? Because Dark Pit is in the game? If Medusa is an echo, is it really that much work that "steal a spot"? I don't think so. Smash Bros roster selection doesn't play like Musical Chairs IMO.
If we have Medusa as an echo of Palutena, it's still "two characters" technically... And people can hide echoes if they bother them.
I get that Dark Pit could bother people because it's Pit... with another color scheme. And we weren't sure he was a bonus at that point. But now, he is just a "side character" that pleases fan without taking space.
Also, despite this, it didn't stopped people from wanting KI characters in the ballot, it's estimated that Viridi did quite well after all.
I may be biased for KI, but almost every character have something to bring in Smash. There's character I don't care about or even dislike (like Falco) but it's still a great addition to the roster.