Because they don’t talk about the internal challenges of the Hero.
James Bond is always sure about everything that he is doing and doesn’t put a foot wrong.
Compare that with great stories like The Pursuit of Happyness, Kung Fu Panda, or Interstellar – the hero always has self-doubts! The Hero faces both external AND internal challenges.
Po was worried about Tai Lung, the evil snow leopard who would bring violence to the world. (External difficulty)
Po is also worried as he is the chosen one who needs to step up and defeat Tai Lung. He has zero confidence in his abilities. His friends and teacher have already given up on him. (Internal difficulty)
When you write a story, show the internal conflict. It’s the hallmark of a good story. We don’t need more James Bonds. We need cute Pandas who are unsure about themselves.