Space him out with projectiles before punishing a whiffed Side B
Captain Falcon has a similar moveset to Ganondorf and like with ganondorf if they try to falcon punch you, go for the counter.
Expect side b, grab, and nair most in the neutral, so bait each out with whatever your character has to offer like disjoints, projectiles, dash back, spotdodge, etc and keep in mind that falcon is fairly easy combo food.
ROCKCROCKING. Basically punishing his up b recovery by teching it off a wall (if the stage has it) into an easy edgeguard (or just intercept it with a safe aerial if they recover at a bad angle)
Falcon doesn't have much against shield pressure behind him, or many great out of shield options in general. Nair doesn't hit behind him and can sometimes whiff on really small characters (Pichu privilege). Up b has quite a bit of startup on the ground and can be reacted to and can be easily punished. Grab is fast but only in front of Falcon.
In general Falcon's disadvantage is pretty bad so once you force him into it try to keep him there.