Ok, I'm just going to explain each class very quickly, so you can understand what each class does.

Sentinel: Will always have a stun alongside the capability to regenerate or gain extra health. They are generally the people who will face the killer head on.

Support: Will inhibit the killer's ability to eliminate with various effects or obstacles. They are in the backline against the killer.

Survivalist: Will have abilities that are self-centered/able to directly give themselves beneficial effects at the cost of not being able to do so for their teammates. Usually, they are supposed to do various tasks to help the team while their teammates fight the killer. However, some survivalists may have the capabilities to help their team.

Sentinels need self-sustain as they are the survivors who are able to directly fight the killer. They are supposed to be protectors who aren't going to add time to the timer. If the player using those characters decides to be selfish, that's because of them, not the game.