OS, you could also.. you know.. bait the bair, and gimp. Mk can adapt just as easily off stage
You can also powershield snake's f-tilt and f-tilt him back with Metaknight, but that doesn't mean it works 100% of the time.
If people haven't figured out that there is a gap in MK's planking by now, they haven't looked. You are forced to stay on the ledge for a certain amount of time, and to grab the ledge the fastest you have to u-air at very certain intervals. There's a gap inbetween these two that you can only cover by u-airing early (in which case you could literally be d-smashed from the stage) or fast falling, in which case you've put pressure on him. Most MKs just do the same two u-airs, regrab the ledge, repeat. This is why you don't see MK drop off the ledge with a u-air, jump (hint, there's lag during the jump where he can't u-air), and then u-air a zillion times before reaching the ledge. Its because it isn't safe. Its clunky and cumbersome and makes MKs feel vulnerable. No one likes to do things that can be punished.
Kel did it to Shugo. Shugo figured it out
mid match because he's good. Unfortunately for Shugo, Shugo didn't know exactly what to do and decided to kamikaze with a dair, killing Kel and barely missing the ledge himself. Had he baired at the same instant he'd have stage spiked Kel without dying himself.
No one said it was
easy. It's not. Falco ****ing sucks on the ledge. He's a garbage character because of it. If you're character is good on the ledge, you get a % lead and you have a good chance of beating Falco. This is not the case with just about every other character in the game. People just care about Falco because he excels at everything else in the entire game. Literally, everything. Combos, kill power, fall speed, grab game, projectiles, anti-camping reflector, manueverability, range, safe approaches, safe evasive manuevers, mindgame potential, a flippin sweet taunt and excellent jumps. Bird just can't deal with being at the ledge or underneath it. So, you abuse it.
Just like you abuse the fact that DK can't do crap against you if you run away and spam projectiles all day, or that G&W's approach sucks if you've got any moves with invincibility frames and/or a disjointed hitbox (hellooooooooo Marth).
If you're G&W and you're getting bum ****ed by a slew of Marth mains that are smart enough to abuse your weakness, your best bet is
not to complain about Marth's range and say "Marth is gay". It is better in fact to acknowledge Marth's inherent weaknesses, like his recovery, lack of projectiles, and commitment to any actual dangerous approach, and use these weaknesses to your advantage by drastically altering your character's natural playstyle or picking up a secondary.
But if you're FALCO, and you realize that you can't do **** on the ledge, you've either gotta go get a Ph.D. in ledge play for your character to compete with the Metaknight with a GED or you need to get a new character. Those are your only legitimate options.
Not being a 7 year old boy with a runny nose saying "that's not fair" to the bigger, stronger 9 year old.