Hmmm .. that’s surprising. It’s possible that your phone is defective or at least performing marginally. I would certainly schedule a Genius Bar appointment to have the unit diagnosed. I’m sorry you are experiencing such poor performance and hope you are able to improve it.I've done it a myriad of ways at this point
Low light, no light, lots of light. With glasses without glasses, staring at the camera intently, looking at the phone normally. Close to my face, far from my face. And of course various combinations of those attempts.