Fox is the best character in the game.
He has the best run speed in the game, best jump speed and best fall speed.
He is short and smaller than most characters and is thus harder to hit.
He has the best move in the game (Shine) and 3 of the undisputed best kill moves (Shine, Usmash, Uair).
His Uthrow is likely the best throw in the game, because of its function (throws you straight up with No lasers to DI), because of Foxes moveset (immense potential to kill off the top or off the sides once you're in the air), and because of Fox's mobility (again his speed gives him so many options once he is underneath you).
His UpB is the best recovery move in the game. It sweet spots easily, can get you back from almost anywhere, burns when it's starting, burns under shields and complicates edgeguarding a lot (when placed properly in each specific match up), combos into Uair's if you get hit by it, lands completely lagless. His ForwardB is also incredibly versatile and can be edge cancelled or shortened. The fact that he has these two moves and that both have so much range and variability, and he has a disgustingly good fall speed, give him the best recovery in a game which revolves super hard around edge stuff. Also his wall jump/scar jumping stuff is insane coverage and again, his UpB makes it possible to cover almost anywhere and still get back.
His lasers are the best camping tool in the game. Anytime he feels pressured or is behind he can always run away and shoot sparse lasers or flat out double laser camp you. Short of planking he can almost always force you to approach. Again, his speed makes this possible and (if played correctly) he can run away indefinitely from most of the cast just by correctly utilizing the platforms.
The updated shield dropping techniques make it incredibly dangerous to even try to hit while he is on a platform, especially if he can just shield last second and drop through into a drill.
Dair is insane. Who cares if they can SDI drill? You only need one of the last hits to connect in order for you to shine -> free grab vs most of the cast or shine -> knockdown at the least, which again, his run speed lets you abuse.
People just need to learn to understand how good speed is in this game. JPOBS occasionally says good stuff but in general says quite a few things that I don't agree with that make me kinda think he's just full of hot air. I don't disagree that we occasionally go through these stages of denied belief about stuff, but I'm pretty sure anyone arguing that Fox isn't the best is just not looking at the full moveset.