If you are used to a stick shift car, the issue is that the left foot is too 'heavy' and totally lacks the sensitivity to apply the brake.

At least that was my experience. I drove an automatic for the first time some years ago, and that was the only issue I detected.

The fact that you never have to move your feet from the corresponding pedals actually helps to avoid mixing up pedals.

It would be an issue in a rally when downshifts require a bit of throttle and you have to use two feet for three pedals.