What? Climbing is super easy.
In Gang Beasts, Human Fall Flat, basically any other game with this type of controls/gameplay, you would need to worry about each arm individually. The left trigger would control the left arm, and the right trigger would control the right arm, and to climb, you would have to alternate.
They already greatly simplified climbing. It's as easy as it can get now. Don't have to worry about left/right at all.
Just have to grab and press the up button. Seriously, how does it get any easier than that?
You don't want to get rid of the need to hold the up button because if you did that, people would start automatically climbing everything they grabbed onto, and that's not always what people want to do. Sometimes people just want to grab, for example the rope on the bridge, so that they don't fall off of the bridge, but without climbing, because if they started to climb the rope, then they would fall off the bridge.
Once again, as in most of these threads, the game is perfect the way it is.
Also climbing up onto ice is meant to be tricky. Ice is slippery.