Well I mean that's great for you but on a generalist level, taking into account all the kids, casuals and everyone in between when it comes to the Smash Bros fanbase, Fire Emblem appeals to only a small niche in a much larger pie. More people from all levels of fandom would get more excited over someone like Midna, Decidueye, Dixie Kong or Shadow than someone like Ceclia.
Even with the nearly two decades of Fire Emblem using Smash as a promotion vehicle, FE has yet to break out of it's status as a niche franchise. FE was selling so poorly in the late 2000's that it was going to get canceled if Awakening didn't sell, but then FE:A acts like a shot in the arm to the franchise and suddenly it's popular! But even it's best selling title, FE Fates caps out at around 2M sales on the 3DS, while Splatoon sold nearly 6M on the Wii U, a console with waaayy fewer owners than the 3DS.
I think that's what really gets me about the amount of FE in Smash, FE isn't as popular as AC, or Kirby or Metroid or Star Fox, yet has way more characters than any of them and people are somehow asking for more. It baffles me. If a character should get in Smash just because their game recently came out then I want Marina, Agent 4, DJ Octavio annnnnd Judd as fighters.