My shooting buddy recently took up close range (some targets barely 10 feet away), rapid fire .22lr pistol and rifle competition. I tried it using a reflex red dot sight and was slower on the first shot. After the first shot, I had acquired the red dot position and was faster on the remaining shots.
Using my pistol, he was faster on the first shot and slightly slower on the following shots. He's faster all around than I am.
For self/home defense practice, I use pistols with open sights and do not use the sights for the first two shots. I shoot them like I'm pointing my finger, then go to the sights. Up to ten yards, those first two shots are always in the main body mass of the target. After 70+ years of shooting like that, it has become instinctive.
All of my home defense and carry guns have open sights.