The child is filled with Hate, Fear, Anger, Resentment, Hurt, and Pain.
They split off from their personality to help them cope with their trauma, in doing this they bury their bad feelings. Which manifest as a monster within their mind.
They go into fantasy mode to create a world that is beautiful, and everyone in this world is beautiful.
The Inner child concept only makes their mind worse, it promotes the adult to stay stuck in their past with their Inner child.
The problem starts from the adult not accepting the reality of what actual happened in their childhood.
Once they accept their bad feelings, and the reality of their childhood.
There is no need to keep revisiting their past, they can let go of their trauma in peace. And stay in their present moment,
rediscovering who they are without having to go back to their childhood.
Adults are not children, and they need to understand this. They only behave like children, when they are stuck in their childhood trauma.