Well Samuel Taylor Coleridge was addicted to opium, of course, yet wrote some brilliant stuff. “Kubla Khan” was probably the first poem at school that I learned by heart for the fun of it, instead of to pass a test!
But yes, when I was reading submissions from the slush pile, sometimes I did seriously wonder what the author had been imbibing while writing. Books that began with a reasonable premise, then wandered off into something totally different.In one book the first half of the story had a ghost character which was quite entertaining, then in the middle of the book the ghost just disappeared and was never heard from again. Or books where part one had absolutely no connection to part two. That type of thing.
Which is why it’s absolutely essential that authors have their book critiqued by someone with a good grasp of both grammar and story-telling. I cannot emphasize often enough that the book you submit to a publisher or agent needs to be polished as shiny as you can possibly make it. Publishers and agents read hundreds of books. Yours needs to stand out for its excellence, not for its “What on Earth?” factor.