I have two 13 pro max iPhones and neither of them show any water color effects with the images it takes. I can’t even force my images to look bad. Most of what is described here in this thread is an issue of user error and or low information photography skills, yeah I know not everyone knows everything about photograph, it’s been my hobby and profession for many years. I think if people took the time to make the necessary adjustments to the camera before the photo is taken, there probably would be less complaints. I’d fail if this thread was about being a diesel mechanic, I don’t know anything about that. Sure there may be a glitch here or there, but those glitches are rare and random. If you use a dslr like Nikon, Sony, canon, etc, then you’ll know to apply the same technique and settings you use on the camera with the iPhone. If anyone just opens the camera on the iPhone and just aims and takes a shot without making any adjustments to the exposure, highlights or shadows etc, then yes, bad looking shots will be the result. You can’t expect the camera and software to do everything for you, the camera is just a tool. And in the hands of a skilled photographer, the photos are exceptionally great! As for the regular 13 and 13 mini, I don’t have any experience with the cameras on those models.
So get the 13 pro or pro max, the cameras are fantastic. I can provide plenty of samples if needed.