I don't think people understand how important movement speed is in this game.
The slowest characters in the game, Ganon, Zelda, Dedede, etc. can literally just get zoned out by some characters.
When your character moves slow as balls you're able to get away with so much stuff that shouldn't be safe but is.
In Dedede's case he at least has an amazing grab, so you can't just poke his shield safely all day.
Ganon and Zelda have some of the worst grabs in the game, so this makes shield grabbing and running in to punish some things really hard for them sometimes.
Falcon being the second fastest at least allows him to get in on OR run away from his opponent.
I mean yeah his options are fairly ****ty when he does get in but I think actually being able to get in is more important in the long run.
Imo having more reliable options(even if they are bad) is better than having big, dumb, strong hitboxes that are easily avoidable.
I just think you'd have to play really smart and patiently to actually be effective with Falcon.