Some characters are just better suited to combating campers, but there's always a way through your opponent's strategy.
Characters like Zelda and Mario that has a way to reflect projectiles back can put a huge damper on campers if played correctly. Faster characters without ranged attacks such as Falcon and Little Mac are forced to approach but can generally get in the campers face and punish them.
It all really depends on the matchup and your opponent. Characters just are better at fighting some and worse at others. As Link, I usually have a fairly easy time with Marth and Lucina but one who knows how to perfectly time their counter can be a problem. The matchup may not be in your favor, but you need to watch you opponent; once you get a feel for the camper's playstyle, you'll notice patterns you can exploit.