My problem with Fire Emblem in Smash Bros. is that despite the amount of characters we have, the franchise is so poorly represented as a whole.
Just by game counts, we have 3 characters from Awakening alone. Gaiden, Genealogy, Tharcia, Sacred Stones be fucked.
You have a ton of different types of weapons and classes, but all they can come up with is swords and swords with something else to compensate. Even worse when they don't fully commit to it with their existing characters. Ike can handle swords and axes, why can't he have a hammer on top of Ragnell.
For all the diversity of characters with this 20+ year old franchise, we get mostly pretty similar looking protagonists, in a franchise where sometimes not even they are the best representative or the most popular character. Heck Byleth is the third avatar we have from a series known for characters, their personalities and interactions.
Stages are all fairly generic and blend too much with each other, we have a coliseum from general FE on top of a coliseum from Awakening. Stages granted is not an issue exclusive to FE, but it applies.
I would be fine with 8 characters from FE if they actually managed to represent its legacy and diversity, as it is, is pretty poor.
About the too many sword users comment, is more so for me the fact that a lot are pretty similar in feel and aesthetic, because it doesn't help that we have 3 Links and multiple incarnations of Marth in these games, that overshadow the sword users that actually feel pretty different and unique.