I'm reading a science fiction trilogy right now which has begun to annoy me. It has a great plot and an interesting protagonist, but the story itself is told via a litany of social justice issues. It's as if the author had a list while she was writing and went down it, item by item, until she had thoroughly covered them all. I could play a drinking game to this series - "Drink a shot every time the author beats you over the head with her ideology," - but I'd end up in the hospital with alcohol poisoning.
Mind you, I'm good with fiction which has embedded messages, but I'm not good with message fiction. There's a difference. All fiction carries the imprint of its author's mind, just as all children carry the DNA of their parents. That imprint is sometimes ideological, which is perfectly all right. The problem arises when an author goes too far down the "I want this story to make a point" road. In those cases, it doesn't take long for readers to spot the preacher behind the curtain, and that's right about the time the author loses a fair percentage of her readership. People don't want to go to church when they sit down to read. All that dressing up and hard pews and sermonizing and waiting for the end so you can have a coffee and danish and talk to Mrs. Jones; it's exhausting.
That said, I do think it's possible to have a message in mind while you're writing. You just have to be careful about the way you execute it. In "Black the Wound, Bright the Scar," for instance, I wanted to explore the ways people deal with emotional trauma, so I wrote about three characters who were at different points on the trauma continuum; a woman who was deeply scarred, a man who was on his way to becoming deeply scarred, and a boy on the threshold of manhood with PTSD. But it was a piece of fiction, not the DSM-5, and I knew the story itself had to come first. I also know that when I lose that understanding, I lose the story.
Why? Because story doesn't work the way sermonizing does. It's a sly, sideways creature that slips in the kitchen door, grabs a leftover biscuit, and comes to whisper in your ear while you dream. Then, when you wake up and remember lava fairies that live in the bellies of volcanoes and men hiding under the bed because of the demons coming after them, you have to decide what all that stuff means.
So that's why I'm perfectly comfortable bringing my self and my life experience to my pen, but I'm not comfortable writing message fiction. I'm not going to feed carrots to the cats in my stories because I'm vegan, and I'm not going to make all of my characters queer because I'm bisexual (though I do like writing queer characters quite a bit). If I'm doing my job right, you won't miss the biscuit my story snitched, and you'll come to your own conclusion about what it means. And that's the way I think it should be.