In any good game, every valid strategy has a valid counter. If camping doesn’t have a valid counter, then that just means it’s not a very well designed game.
For instance in CSGO, “camping” is one of the main parts of the game for both teams during different phases of each round. There are dozens of strategies to clear campers out. You can lob a grenade, throw a flashbang, or throw a smoke to block their potential line of sight. You can send in two or more people at the same time to try to overwhelm them. You can wait til you hear them reload or unscope or walk away. You can try to come at the site from a different angle and get a flank on them.
Most of the time I find that if people are getting killed over and over to campers when so many valid strategies exist, it’s less that the other person is camping and more so that you can’t overcome that.
I forget which map it was, but Battlefield: Bad Company 2 had a particularly broken area where a medic class (machine gun and 4x scope) and assault class (ammo drop) could pin down the opposing team at their spawn point, from a distance, indefinitely.
Took me and a buddy around a minute to find it, so we weren’t doing something particularly unusual.
Good design could have rendered this tactic inoperable. I don’t know if it ever came.
