The way you come up with ideas on how to break, red team and exploit; when to do this and how to stop: that part is not objective. The machine can't do this for you sufficiently well. There is a subjective process in there that you're not acknowledging.
It's a good approach! It's just more 'negative space' than direct.
People who pentest spend more time running a playbook than puzzling over the logical problem of how to break a piece of software. Even a lot of zero days are more about knowing a pattern and mass scanning for it across a lot of code than playing chess vs a codebase and winning.