Firstly, if you stop all human input into AI and have AI only output based on other AI output you will never generate anything new in a trillion years, it just regresses into variations of the original human input before it was stopped. It will never evolve as humans do as it is just a statistical trick at the end of the day.
Secodly, humans take only a few examples while AI needs trillions. AI built on a few examples would not have enough data.