How would you guys feel if every character returned from the past game and...
Pichu became at least semi-clone due to balance reasons,
Young Link became a semi-clone of Link, making him even more different than Toon Link,
The Pokémon Trainer becomes a glorified random button for Squirtle, Ivysaur and Charizard, gaining his own winning animations, and automatically switching Pokémon each time one gets KOed. Choosing a Squirtle, Ivysaur, and Charizard will allow you to play as that Pokémon the whole match,
Squirtle gets a new down special,
Ivysaur gets a new down special,
Dark Pit became a semi-clone of Pit, and is more power based,
and Lucina became a semi-clone, and has more KO power.
Mii Mage added with a bunch of moves taken from Zelda, Black Mage, and Palutena. Each Mii class became a default moveset, with the Custom Miis being fully customizable. You can change their weapon, animations, attacks, stats, and even their trophy pose. Each available attack is shared with at least one other fighter in the roster, but you can mix and match as much as you want for maximum uniqueness. (I can put more detail into it in another post if you want.)
On top of that we got the following newcomers (Disregaurding the fact they could be future DLC, and that new franchises could pop up later):
Inkling
King K. Rool
Impa
Chibi-Robo
Takamaru
Xenoblade Chronicles X character
Fire Emblem Fates character
Next Gen. Pokémon
Black Mage
Paper Mario
Isaac
and one or two others.