@vanilla1016
Cause he's still a child.
Think about it. He was cursed when he was child with insomnia. He literally couldn't sleep or even pass out unconscious. That mean he never had that chance to grow his child mind to an adult mind because a whole army of negative emotions was ravaging his mind till he met the MC. Sure, he can make adult decisions for the good of his country, but for his own personal growth?
He is growing though.. but that's also being restricted by the MC who stupidly believes the book she is in is still going to follow the same storyline. She has rewritten the fates of so many people and she knows this, but she still thinks this book plotline is still relevant.