This is exactly my problem. 100%. It manifests in the iPhone 7 and iPhone X which I have. I also was able to acquire a 13 because I thought those 2 phones cannot handle iOS 15 anymore but annoyingly, said issues are also present on the 13 phone.
Again, this is a genuine and legitimate problems. Please Apple, fix this.
Summary of Problems:
1) Thumbnails of images in the Photos app and any other app where you have to choose a photo, they are blurred and pixelized.
2) Upon taking a photo in the Camera app and immediately viewing them takes somewhere from 5-15 seconds for the image to load. During that time where it loads, the image is completely blurred and pixelated and cannot even interact with the image.
Again, this is a genuine and real issue. Apple please fix this. Have been sending Feedback through the Feedback app as well before during the betas and no results really being seen so far.
Also, iCloud Photos is off