There is no point since like you said, a much cheaper phone will do everything you just said. All the stuff you said was just to sell the new iphone.
Well, there is a point, you just don't necessarily agree with it.
The point is that 10-15 years ago you could easily have spent £800 on four separate devices that still didn't do everything a modern smartphone does.
And besides, I conceded that you needn't spend £800 on a phone. You could spend a lot less, but it certainly wouldn't necessarily be as good at all of those things as a high end smartphone.