You're complaining about ledge camping while using Marth?
better learn to spam dtilt. There really is a lot of things characters can do...
Metaknight, i.e. Cobalt can jump off the stage, airdodge through you then uair. MANLY. and it works.
Falco, i.e. not Cobalt can like... pew pew laser and cry ;_;.
Also the way you play can promote the opponent to ledge camp. Juggling an opponent, in other words, keeping them above the stage instead of off/to the side means? They go for an edge you're hitting them back up again. Over, and over, and over. What can they do? They have to get firmly on the ground, but you're smart enough to definitely cover the closest edge to rehit them.
Snake can plant a grenade, a c4, and spam usmash, and he can have all three go off at different times.
Oh yeah, this is about ledge camping, not stalling. But I don't usually see much difference unless I'm playing a CHARACTER THAT CAN'T HANDLE IT. I'm not even sure what character this ledge camper is using, but if it's a Pit spamming arrows on said ledge -> it's not stalling.