Let me put it to you a different way, anyone who knows what causes this knows how to fix it, iPhone or otherwise. Anyone who doesn't, probably doesn't care much about photography anyway, so it's hardly a "key feature".
This is like arguing that when reflected light hits your eyes it's bright, and that's a failure on whoever designed your eyes.
So it's no big deal when a phone is affected by flaring and hazing at mich wider angles than EVERY other phone, and when you get flares, they get bigger with a bigger hazing area that's far more pronounced and when you don't have flaring but you have the sun hiting on the phone from the side, you get hazing all across the side of the image. something again, no other phone shows.
Yes the flaring happens on everything, and the hazing with sun hitting the phone while not being in the picture happens on old phones with bad scratchy plastic lenses. but the flaring and hazing isn't even remotely as bad or easy to get on other phones.
Yes it's avoidable. BUT it's a phone, it's a instant point and shoot camera. it's not a DSLR. it's not there for you to compose great shoots. it's there to take goods pictures of what's happening around you. without you needing to worry about composting or having to stand this way while tilting over sideways and holding your hand at an awkward angle to shade the sun, and moving the phone a little more to not have the hand in the picture and sacrificing two virgins while burning black devil candles on a pentagram while.... oh ooops. the kids stopped doing that funny thing you where going to take a picture of about 5 minutes ago.
To bad you had an iphone so instead of taking a photo right away, maybe with a small flare up int he corner, your picture is instead half covered in a flare, and the other half is badly tinted purple and you can't see what's going on. But hey, this flaring and hazing is no big deal and won't affect anyone...