LOL.. indeed.
Although I'm not talking about style, I'm talking about content. For instance, a documentary image may be in a similar style as someone else's, and it may be for argument's sake, an image of a person, so it would be easy to say therefore it's not unique, but what matters is the subject matter. If it's a documentary on something unique, then it's unique.
Besides, as you say, there's nothing left in the world that's not been photographed, but you could also level the same accusation at painting: There's probably nothing that hasn't already been painted, or drawn... so surely your statement would be equally as true for all art forms? Why does anyone bother then? Why do you bother?
The fact is, subject matters. No one needs to see another shot of Durdle Door, but a landscape shot in a similar style of a place anyone rarely sees WOULD be unique would it not?
No.. they're not., which begs the question why you mentioned the 'uniqueness' of them. They're unique in style.. to an extent.... meaning it's rarely seen and a rare skill being brought to bare, but that's only of limited appeal. Once these artists have had some recognition, they'll fade away as artists unless they DO create something unique. People get bored easily, and will move on to the next Facebook post that will "Blow your mind when you read this".
People have incredibly short attention spans these days.