In true wilderness untouched by man or by man made gear and equipment, pliers have few uses. Mainly removing quils, thorns and splinters, and perhaps cracking nuts.

Most of us venturing into the wildnernes will however have a fair bit of modern gear and equipment, and pliers are useful for all sorts of repairs and improvisations.
Bending or straightening hooks and D rings, holding items in or near a fire, unsticking zippers and pulling out nails come to mind.
Very useful for fire lighting IME as the pliers permit of tinder etc being placed exactly where required without burning the fingers.
Also useful for crunching up small sticks or pieces of wood into very small, matchstick sized pieces for fire lighting.
Just yesterday I used the pliers of a Leatherman tool to open a ring pull can of food from which the ring had come off. This was indoors, but could just as well happened in the outdoors. Opening the can with only a knife would not have been easy with some risk of damage to both knbife and user.

Plier based multi tools are of course very useful in the built enviroment, and the best survival tool is the one that you have with you. He who is used to ECDing a Leatherman tool or equivalent will probably have it with him "by default" in the great outdoors.