What are you guys talking about? Don't you remember the riots in the streets that occurred when K.Rool got announced and no one knew who he was?
Seriously, going to be blunt here, I play alot with casual friends (or atleast did when we still could) or just random people at parties. People who aren't really Nintendo/Smash fans or big gamers in general. Most of them, believe it or not, don't care who gets in! They don't know who half these clowns on the roster are as it is! But they don't care, because the game is fun and accessible. And it's not like the first pass appealed to the mainstream gaming crowd at all either, 3 JRPG characters, a niche (BY MAINSTREAM STANDARDS) fighting game character, and one they probably knew as "oh, that guy people REALLY wanted in Smash, Microsoft bought them and put them in that car game right?"
I'll admit, most of the first party leftovers (aside from Waluigi, who's meme status has reached mainstream) and third parties more heavily associated with the Nintendo fanbase (IE: Shantae, Rayman) are less popular once you venture outside of the Nintendo sphere, that's fair. But you know who people outside of that really seem to want? Based on what I see, it's always the big third parties, Crash, Master Chief, Steve, Doomguy are just some of the names I see that keep coming up from people who aren't really that interested in Nintendo or Smash. If only there was... some kind of overlap here... where Nintendo could somehow pick a character... that could appeal to both groups... Nah, it's not like Smash fans care about Crash or Doomguy or anything.