Ironically, I write sci-fi because there's no sci-fi out there that I personally enjoy reading. I mean, I can wade through it, but there's no sci-fi for me, if that makes any sense.
There are a number of ways someone might approach SF / Fantasy: they could be a "fan" and simply
enjoy reading it and never feel any need to write it, they could be a critic or study it from an
intellectual, historical or sociological approach and perhaps not "enjoy" it in a so-called fanboy sense (even not caring much rather than to study who was the first author to write about a mechanical man that could pass as human, etc).
I certainly see how someone could feel a drive to
create SF / Fantasy for their own artistic fulfillment and self-expression ... and still not "enjoy" reading huge amounts of it themselves.
I'd suppose any writer needs to know about their market, have a grasp of what's been done already. But then I could also see someone sitting down and writing "a love story about vampires" and having a hugely successful novel ... having only seen a "Dracula" movie.
Sometimes we may
overthink things. Most genre fans aren't overthinking, or thinking much at all perhaps.
Success is based on others'
"enjoyment" ... and achieving that perhaps need not require any great technical flourishes from the writing or the writer.
Simply ... tell a good
Story, and don't tell it
badly.