...quality to writing that's independant of vocabulary and other colloquial structures, a quality that - even if using neutral/average vocabulary - renders a writing interesting? Is it grammar and excellent ratio of cohesion/coherence? And if not, where does this quality reside? In using varied and highly specific vocabulary in proper contexts? In voice and tone of writing? And if so, how is one to develop such? By emulating authors that are nearest to the voice you want to develop?
I'm not sure it's something that you can nail down - especially when it comes to voice and tone. But I think with voice it's really about finding your own internal voice and way of thinking, then letting it leak onto the page. That's how you get to be different from everyone else. Granted, it's good to read the stuff you like and want to emulate. I stole a lot of my worldbuilding and viewpoint technique from Michael Chabon's The Yiddish Policemen's Union, my cast-building a bit from Gene Rodenberry, Shonda Rimes, and Aaron Sorkin - a lot of plot stuff from Asimov's Foundation, and maybe a tiny bit of voice from Anthony Bourdain. But even with that, the "secret sauce" that makes the voice tick isn't any one of those things, it's in the mix of all those divergent things combining to make something new. And all of that gets filtered through my own point of view on life - which is my case is a cheeky, sarcastic, and often cynical view of Washington DC, politics, journalism, and the toxicity of ambition - the type of view one can only really develop from actually existing inside the Washington political machine and seeing how messed up it is first hand. So, yeah, look at your influences. But also look at yourself and what makes the way you look at the world different from the way people around you view the world - and why. That is really what makes a voice for me.
I think being understood can be a criterion for quality. If no one understands your words and/or sentence structure, no one can judge and interpret your work. After all, art is a form of communication.
I don't think there is any one answer to this question. If words were Legos.... Arthur C. Clarke would build you an awesome spaceship with only a small number of bricks and those bricks would all be of the old-school kind. No fancy-schmancy pieces that only ever seem to have just one purpose. He was a master of making due with simplicity and economy. China Miéville will also build you a fantastic ship, but he uses the really expensive Legos that come in the big boxes and have very highly specialized pieces. Samuel R. Delany wasn't one to use the fancy pieces either, just the basic ones, but his spaceship doesn't look like anyone else's spaceship and he puts his pieces together in odd, unintuitive arrangements. To appreciate the mastery of his work, you have to accept that a ship can look like many different things.
Im not a big fan of wordy text. Its starts to become pretentious after awhile. I like the way people use regular words to make them interesting or redefine words or create new phrases. This is a great example. You were able to be very descriptive while using regular words.
I think quality lies in intent ( context ), arrangement ( style ), and rhythm ( word choice. ) No big words necessary. You take the 23rd Psalm or the Lord's Prayer for instance - very ordinary words transformed into majestic imagery. Made even more powerful by the rhythm. No sentence is too tricky. And it has just enough metaphors to give visual clarity to the promises in each prayer. The techniques used are quite easy to emulate. Take the Lord's prayer it employs - rhyming and repetition - super easy, while the 23rd Psalm creates a pattern with its sentences - first part of the sentence - is the promise - and the second half of the sentence - how it's achieved. Kinda reversing the order of cause and effect. But even if your prose doesn't have a powerful context/content behind it can still be quality. I would research writing you like and admire. See how they construct a scene. Write small things that you can edit so you can see the process of taking an idea and clarifying it. Read poetry to develop an ear for rhythm. And be bold. A lot of weak writing comes a lack of confidence in what the writer has to say.
"Is there a general ...quality to writing that's (...) renders a writing interesting? Is it grammar (...)?" Have you ever found a book interesting because of the grammar?