So I thought I'd weigh in.
Let me (why should you be surprised at this, I am a writer!) tell you a story.
A long time ago in a galaxy far, far away... no, wait a minute, that's another story.
The story, now. The REAL story.
My first published work, of which I am still very proud, is a slim booklet of three... I don't know what to call them... fables? Fairy tales? Stories of the fantastic...? THink of Oscar WIlde's fairy tales (The Nightingale and the ROse, The Fisherman's Soul, that type of thing). That's going to get you very close to what these sotries are. I wrote them clandestinely, I remember scribbling this wildly imaginative rather sad poignant and very lush tale on a notebook hidden under a large Biochemistry text which I was supposed to be studying from for an exam - and every time Momma walked into the room for anything, like a totally juvenile kid about half my age, I would guiltily slam the textbook down on my flight of fancy and pretend I was Studying Really Hard. When I was notified that Longman UK wanted to publish these three stories together in a book, I kept on thinking, in an anthology, with other people, and they kept on saying, no, YOU. *Your* book. When that finally got through I kind of fizzed out and breathed the rarifed air of a plane of existence I never dremead was possible, an air with a scent to it which I have never forgotten, a perfume of pure and unalloyed disbelieving joy.
But - and you heard that coming, didn't you. There was a "but" looming.
I write lush, okay? I was accused of swallowing a dictionary when I was five, which, for someone whose first language is NOT actually English, I took as a huge compliment, and still consider as such. These stories contained worsd like "raiment", and "naught", and "succour", and "plaintive", and "admonished", and "palfrey", and "meandered" and "irrevocable" and "unerring" and "forsooth" and "Vagabond" and "poignant" and "extolling" and "fragrance" and "physicians". You get the idea. These were fairy tales written for an adult reader, with an adult vocabulary, using words which your average kid would find difficult to spell let alone comprehend. And yet... this was a book slated to be published not as commercial venture but as part of a reading series, "The BOok Project", which shaded from books to be read to very young children through early individual readers, intermediate readers, and the bracket that mine was to be published in, advanced independent readers of age range 11-15.
When the proofs arrived for me to look at, I was terrified that they were going to eviscerate these stories, that they were going to go through them with a fine-tooth comb, replace palfreys with horses, replace poignant with sad, replace, in face, all of my rich polysyllabic atmosphere with words that were easier for an 11-year-old to grasp.
You know what...? They didn't. The changed almost nothing at all.
It might have been rich and strange, but it was accessible. Readers taken gently into another world will follow wholly, and if they do not recognise a word which might be beyond their sphere of knowledge the context should be enough to teach that word, or at the very least to render its meaning transparent in various other magical and enchanted ways, in a manner which may leave the reader unable to give a precise dictionary definition of said word but with a pure and perfect understanding of its transcendent meaning and of precisely what the author meant by it.
I'll give you an example of a writer who writes prose luminous with such transcendence - CHina Mieville. He is far from everyone's cup of tea, and I'm prepared to hear lots of arguments as to his "accessibility" - but I love, love, LOVE reading his stuff, even if he didn't tell a rollicking good story in the background of that incandescent language. He makes me reach for the high places. I like reading writers whose work makes me stretch. Any piece of prose can have that magic in it, the quality is far from confined to the speculative fiction genre - but it DOES seem to occur more frequently in Science Fiction and Fantasy, and it's part of the reason why I love reading the stuff.
But this "accessibility" thing - what is it? What does it mean, precisely, both in terms of definition and in that transcendent sense that I was just talkign about? The dictionary defines it as "capable of being understood or appreciated" when applied to writing or art - but the definition of the original word is more graphically just "providing access, capable of being reached, being within reach". In architecture, that word has a precise meaning - how easy is it going to be for handicapped people - folks in wheelchairs, for instance - to access the building. And while this last is not just admirable but essential in a civilised society which recognises all of its members' needs and requirements, I am not sure just how much of it applies - in that most direct way - to things like art. Newspaper stories are "accesible" - but I've heard it defined as pitched at the reading level of a thirteen-year-old, and I don't mean the one who might pick up my fairy tale book, I mean the kind who'd rather be out at batting practice or hanging out at the mall. The kind of teenager that uses "like" as, like, every third word in their, like, conversation.
I don't write for that audience. I never have. I've been told I'm lush and rich and strange and occasionally downright weird, but I've never written down to anyone, nor claimed simplicity was a virtue - in a novel, anyway. Novels are SUPPOSED to be rich and strange and lush and occasionally weird, and full of complexities. How else would they hold my attention or engage my sympathies?
So we get to a crossroads where the actual meaning, the supposed meaning and the yearned-for meaning of the word "accessibility" have been known to go off in mutually exclusive directions. Perhaps the only thing I can offer in terms of something resembling advice is "know your audience". If you're writing, like I am, for people who know and read Shakespeare, Tolkien and Mieville, accessibility is a whole different ballgame than if you're pitching your work at someone who reads little more than the sports pages of the local newsrag. And what it boils down to is, who do you WANT to read you?
No amount of special ramps will make a piece of prose "Accessible" in the sense that a building might be made such. In literature, these training ramps sound awfully like condescension, and are resented (with reason) - people who are intelligent enough to perceive that the ramps are there, and that they are ON them, are righrfully annoyed at being patronised and patted on the back - there, there, you couldn't quite understand how to use the stairs, so we made a nice and *really* smooth low-grade ramp for folks like you, take your time, use the railing, and be careful not to fall. It's a long, long way down.
In writing and reading, I think you find your own level. Accesibility is as accesibility does. People capable of understanding will find you; even people willing to try to understand will brave the stairs on their own. But unlike the architect of a brand new downtown civic attraction, you (the writer) are not obliged to provide special access routes. These hypothetical bulidings of story and dream are not built from bricks and mortar, but from words and ideas. Accesibility might depend on your readers having entered another, different, slightly less complex building than your own BEFORE they attempt to enter yours - I am not saying that writers should ring their "buildings" with moats and install drawbridges and insist on only people with correct passwords be permitted entry - that's starting to smack of elitism and pretentiousness. It is perfectly okay to leave the front door of your edifice unlocked, even wide open. Even if you have put such a door at the top of a steep staircase made of glass, you have done nothing to limit accessibility to it... by people who are willing and able to climb that staircase. And the choice to do so would be theirs, not your own. No amount of bribes and infodumping and condescenscion will make that climb any easier - and enough of such "aids" will make your edifice significantly less inviting to the people who might otherwise have got there unaided.
The doors of my own "houses" are wide open - I invite visitors, welcome them. What treasures they may find in the rooms which they enter, I don't know myself. For every visitor, they are different. That is the wonder of stories. That is their gift and their reward. But nothing precious in this world is free, and the effort of obtaining a prize is sometimes enough of a reward in itself. Speaking for myself, I hope that people who climb my own glass staircases find the view from the top to be worth the trouble taken over the ascent.