The Nikon does minimal post processing. The iPhone throws a metric shit ton of algorithms at the image data to make it passable. For normal people the iPhone output is good enough - though it often looks very over-processed.

Nikon just expects you to handle that post processing part that your iPhone is doing for you. In exchange you get way more control over the final image.

Both devices are aimed at different people. I myself have an iPhone 13 pro and a Nikon Z6ii. I tend to take snapshots with my iPhone because getting out the Nikon + playing around with sliders in Capture One is just too much hassle for a snapshot. Now would I take the iPhone and do a landscape photo where I hiked 6 hours to the photo location at 3 a.m. in the morning? Probably not. ;)