Too deep in the weeds
It’s not about smarts, not about knowledge nor experience….
The best professional could still experience intellectual fatigue when he has been working too long on a system, causing him to overlook obvious issues. Or in certain cases, it might be a clever little adjustment to the product… a slightly altered application of the system, that a new pair of eyes spot readily, that a highly familiar pair may otherwise fail to notice!
A professional that cares to have a better outcome, is always open to finding ways of doing it better… to new ideas… to a new path.
Be open to what others have to say….
Someone new, that is not stuck in the weeds with you, though unfamiliar with your system, could likely offer you fresh perspective.
He does not wear the blinders that the weeds you are stuck in have put on your vision.