Uniqueness in mythology

Here comes a phrase too often heard in a host of works dubbed "medieval fantasy":

"This is inspired by Tolkien".

Here then comes the most common answer to demands of originality, from people fed up by Tolkien's mythology:

"This isn't Tolkien. We are copying Howard instead."

In the same way, every horror writer is inspired by either Wes Craven nowadays, with some Lovecraft thrown in the mix. Similarly, every vampire story takes its roots in Bram Stoker or Anne Rice's works, save perhaps Josh Whedon's series.

Why in the world are we unable to create new and compelling mythologies? Why can't we break from those molds? What is the process required to break away from those molds? Are there not myriads of possible mythologies that could inspire breakthroughs in storytelling? I'm stuck myself in this conundrum, for although the core of the story I'm writing is very promising, and the behind-the-scenes aspects of my mythology is somewhat rarely found in stories, the visual impact of my mythology reeks of "I've played too much WoW/D&D".

I want the world-beyond-the-world in my writings to be unique. I have to stare at Neil Gaiman's The Sandman for hours just to convince myself that it is possible.

The difficult part in this is that recipes, by definition, cannot create something wholly new.

So I ask all my readers: how do you manage to create newness and uniqueness in a mythology? Do you even attempt it? And as readers, do you care?

I will attempt originality in a new cosmology, which works within the world I am crafting for my stories. But before I write out my attempts here, I would love it if one of you could answer the questions above, for yourselves, without any bias interfering through my exposed attempts.

Why everybody slept with everybody.

Exhaustion and overtime work killed my creative juices for the last 2 months, so I took that time to read and watch good fiction instead.

Watching "A Game of Thrones" made me realize an unrealistic component of most good fiction: characters, even ones living halfway across the world, tend to have way more back-story to their relationship than they should realistically have. 

I wasn't doing that at all before, and I now realize that I was wrong. 

This back-story provides an essential part of the fiction you are writing: it makes the characters love or hate each other with unbridled passion. Spectators (and actors, for LARPs/Interactive Theater) will mostly care about characters if the characters themselves are passionate about each other. 

So, if you write a story about 2 war leaders trying to decimate each other's peoples, don't just make them hate each other because they're racist. Have the first protagonist's sister married to the other in the past, and then executed for adultery.

If you want protagonists to bond, they could discover they're brothers and sisters (like Kira and Cagalli from Gundam Seed) or fall in love with relatives (Harry Potter and Ginny, Ron and Hermione). Or maybe the grandfather of one of them had enslaved the other's grandmother, and although that is officially water under the bridge, the 2 protagonists will have a tension that will never let loose, and explode whenever you, as a writer, need it to.

Soaps have run on this stuff for decades, and Opera for centuries. 

If you need convincing, I offer this challenge: read Frank Herbert's Dune, then read Isaac Asimov's Foundation. Notice how dry Asimov's writing is. It is purely intellectual, it is ripe with the ideas of a genius, it is prophetic in many ways (e.g. miniaturization), it is a masterpiece, yet it is extremely hard to give a damn about any of it. Characters don't really care about anyone, so we, as readers, don't either.