It's possible to save RAW files (mostly) unprocessed with iPhones, either via built-in functionality (Pros) or via apps like Halide.

But the aggressiveness of the de-noising in the native JPG/HEIF images otherwise is really unfortunate if you want to look at the images on a screen larger than the phone's screen. The amount of detail lost (other than in areas like people's faces where the phone knows to specialise) can be very considerable.

I'd really like a way to dial that aggressiveness down a fair bit, even at the cost of more noise/grain and larger file size (through less compression due to the extra noise).

Another thing is the amount of lens flare you can get when shooting at the sun for sunsets/rises, etc or other large bright light sources. With very small lens elements, from a physics perspective it's understandable that suppressing the reflections and inter-reflections is very difficult on such a small surface area (even with special coatings to reduce the fresnel reflection ratios), but if you care about image quality and wanting to look at images on screen larger than the phone which took them, larger format cameras still have some benefit despite their larger and heavier size and therefore inconvenience (looks at 5D Mk IV on shelf).