>>280486948
Climbing reliably relies on using the crouch button, trying to climb with just your body is much harder and feels either like you glitched your way up or got lucky with the physics.
You grab what you want to climb, lower your arms to lift yourself, press the crouch button to bring your legs in, crouch in real life for a little extra movement and then move your arms once more to pull yourself forward. Eventually it becomes fairly easy to do consistently, even with objects in your hands. Combine with crouch jumping and you can move around pretty fast.