Focusing on the reverse camera probably does make you worse at reverse parking because it puts your attention on a small part of the overall situation. They’re a nice thing to have as an additional viewpoint in tighter spaces but it’s better to use your side mirrors primarily while also checking regularly on the front of the car and the reverse camera.
I have a new car now and it has one of the reverse cameras, and somehow that makes me worse at parallel parking.
Focusing on the reverse camera probably does make you worse at reverse parking because it puts your attention on a small part of the overall situation. They’re a nice thing to have as an additional viewpoint in tighter spaces but it’s better to use your side mirrors primarily while also checking regularly on the front of the car and the reverse camera.