He said it in an interview.
Which makes sense, considering almost every character can infinite jump, autocancling, the edge hugging, multiple air doges, how nearly ever b move makes you move somewhere in the air now, etc.
The entire game is basically built for air battles.
Except Snake, who instead was given a great anti-air game, with his upsmash, grenades, side special, disjointed uptilt, and how they give his c4 an abnormally large underneath hitbox to ensure snake hits himself back up into the air using it and can gimp those trying to recover low, as well as many characters being able to hit after their upb, giving them great offensive and maneuvering capabilities.