Oh yeah I forgot the 3 most important characters I don't want:
1. Indie characters:
Undertale is probably the most beloved indie game ever and Sans is in Smash as a special Mii Fighter outfit. I don't think any indie character deserves more. Indie series tend to lack history, continued innovation, and most importantly fans and mass appeal. Minecraft was an indie game for instance, but it got history and an impact to become a major force in gaming. The Witcher and Rayman are 2 examples of similar tales. Those series went from being indie to being major video game franchises with a ton of historical importance.
Unless an indie series surpasses the indie title, they don't belong playable in Smash. Smash is a mascot fighter, not a wishlist fighter like some random MUGEN game. Characters should have weight behind their history. We should not be adding a character just because you like ultra skinny chicks.
2. Secondary characters:
Basically no Geno (he's a secondary character in the 3rd most important Mario game from 1996), no characters that are so deep down the cast you gotta look for them (like Anna in Fire Emblem). Smash shouldn't have series' Diddy Kong's before their Donkey Kong's. Respect the Main character status.
Like I said before, Smash is a mascot fighter, and it is better that way.
3. Non-Video game characters:
The reason you don't want Goku isn't that you hate Goku or the idea of him in Smash, it's that you got to work thru like 6 companies to get him in. Then if he's in, if one of them randomly gets mad they can shut down all Smash streams, videos on YouTube, tournaments, ETC. Don't believe me? It all happened to Dragon Ball FighterZ and that killed a lot of that games' competitive momentum. Disney killed Marvel vs. Capcom multiple times in spite of the series' printing money and being genius.
That would not be ideal for Smash, because manga/anime/animation/big companies like Disney can have really terrible PR departments and people in charge, and can throw that legal weight around in ways not even Nintendo can protect themselves from.