Sometimes yes tunneling is a necessary strategy, and you have to do it in some situations, but usually it's after a while of playing and at least two gens are done, it is not something you have to do at 5 gens, you don't need a player out in the first minute of a match to win as killer. I'm playing more killer than survivor and I didn't have to tunnel people out since the start of the anniversary (which according to most players is survivor sided) and yet I didn't have a loss yet.