I believe that once you have established (or even just recognise) your own style and voice and understand what you are doing, you are less influenced by other writers, simply because there's trust and familiarity in your own methods. And that doesn't mean complacency, but rather the confidence to tackle more complex writing and ideas.
Hi! Influence is a living food of which we even have to be aware of its value as a creative and evolutionary motor. It is true that at first the influence of certain authors, those we like the most or with whom we identify, is reflected in a more or less evident way in what we write. It is an unconscious process. Then, in a second stage, we are already a little more capable of even analyzing those authors with a critical eye. Or we can think: "Oh, how creative was in the way to solved the intrigue in this or that way!"
But this happens with people who read as much as they write.
Because, as you say, there are also many who have been writing for years and, in effect, have developed their own voice and style; But, as they do not read, or only read little, they tend to repeat ideas that are already somewhat hackneyed or, worse still, if they have read little about theories and conventions, despite having that internal voice, they also tend to have various errors of coherence, lack of rhythm, ambiguity, poor character development, etc.
And there is even a third case. The mainstream. Writers who, on the contrary, even have a certain reputation, there are others even with awards in their history, and in fact they write very, very well; they obviously don't make the mistakes I mentioned earlier.
But, when these mainstream writers get down to writing
sci-fi, curiously the ideas they put forth have already been covered for the most part, and quite often. Because, obviously, they are experts in the classics, in contemporary literature, in poetry, etc. There are some who even have PhDs in Literature.
But many don't know about
sci-fi, they don't know its rules. That's why it's the fandom tantrum when they win an award that authors belonging to the genre are supposed to win. Of course, those who have won have done so for the unquestionable quality of their stories. Literary quality, I mean. And that is what is rewarded, quality; not so much so the supposed creativity of their ideas or approaches.
For example, this is likely to be the case if a
sci-fi or fantasy writer sets out to write general literature. How many possibilities would there be that a Bolaño, a Faulkner, a Proust, a Chekhov, even an Isabel Allende would appear there?
It occurs to me that perhaps Phil K. Dick and little else.