The announcement that SNK's Terry Bogard is coming to Smash was met with polarized responses. Fans of Himbo's and the King of Fighters series were overjoyed, while fans of not-those-things were somewhat irritated, decrying Terry as just "Ken in a hat." We saw similar split reactions when Banjo Kazooie and Dragon Quest's Hero were revealed to be Smash DLC.
If you love Banjo, you see him as a classic icon of the golden days of 3D platforming. If you don't, then he's just a generic serial box mascot who abuses a bird. If you love Dragon Quest, then Hero represents one of the most storied and influential RPGs of all time. If you've never played Dragon Quest, he's just another sword character "...who looks sort of like Goku I guess."
Between all the joy and bellyaching came the appearance of Sans from Undertale as a Mii costume. This is on top of Shovel Knight and Bomberman being Assist Trophies, Shantae and Risky Boots being Spirits, and Dracula being one of the game's bosses.
Smash is no longer a celebration of Nintendo's history where one or two rivals from a competing publisher may be allowed in as a sign of respect. That's what it felt like when Sonic and Snake were first announced for Brawl. It was a mind-exploding moment that took the franchise to the next level, but that was over ten years ago. Smash has been beyond that level for a while now.