I think part of the problem with writing as opposed to, say, playing the violin is that most people are taught to master the *technical* part of the skill as part of our basic society -- they can use language, read and write words. So the skill gap is less obvious.
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What separates published writers is that they also get good at self-editing, possibly even completely redrafting the entire piece
Beta readers, subject matter experts (including sensitivity readers), agents, and editors all make suggestions to writers, and they sort through those comments, decide which to accept, and how
I would 100% get hunted down and shot by any writer in the fiction world. But I get rave reviews for it
Off my own experience... I'd say that's accurate.