Iphone 7 Plus Photo Quality

I just bought my iPhone 7 plus on Black Friday. Initially, at first glance, with my big shiny screen, the photos I took looked good. I brought the phone to the beach on a cloudy day (perfect lighting) and shot about 100 pics using portrait mode and normal photo mode within the camera app. I took a few more in the house but it was well lit. As soon as I got home, I uploaded the images to my computer. UGH!!!! The pictures are a disaster. I upgraded from a 6 and the indoor images looked as if they were taken with my 6 selfie cam. Totally pixelated. I have another image where my son is missing his nose. The beach photos look as if they were PAINTED - a watercolor effect and NOT sharp. I took my phone into the Genius Bar today and the guy helping me agreed the photos were not good quality. He pulled out a test iPhone 7 plus and snapped a picture...again at first glance they look ok. Zoom in and it looks like a watercolor painting. I ended up leaving with no resolution except he thought it might be a software issue that apple will hopefully fix. I have about 8 days to return this phone if necessary. Some of the reports I'm hearing are that it's SOME phones. I'm wondering if it's ALL and people haven't uploaded yet or zoomed in. Photos taken in instagram seem fine. Using LIGHTROOM app to take photos is an improvement for sure but still not great. Is anyone else experiencing this? I don't want to hang onto a $900 phone just HOPING Apple will fix this issue. After all, the only reason to spend the money on the upgrade is for the camera Apple was boasting about.