My problem with any KI newcomers apart from Palutena is that they're all greek myths, not Nintendo IPs.
Medusa and Hades. The first versions of those that come to my head when I hear those names are not "Nintendo" or any Nintendo related games, but Disney Hercules and other Greek myths. And plus, Dark Pit. Really? There's a difference between "doing a Lucina" and having a clone character, but there would be LITERALLY no difference between Pit and Dark Pit (or Pitooey). Whereas Marth and Lucina are seperate characters in seperate games, Dark Pit is literally just Pit with an attitude problem.