Someone on a discussion site asked the above question, and I figured it would make something to write about here. One reason I thought my thoughts on the matter were better suited for this page is that I don't write fiction, so I don't think person was referring to the kind of writing I do (whether that's business writing, personal writing, killing-time writing, serious writing, or any other kind of writing that I do for one reason or another).
Maybe this doesn't really apply to me because I don't write fiction and stopped reading fiction once I had children and had to make sure that I made the best/most productive use whatever reading time I could make. So, while I read all kinds of things (non-fiction/fiction before having children - and kind of felt like I'd more than covered quite a bit of reading), I trimmed out fiction (but added children's stories as part of shared reading time (certainly not my private reading time).
Anyway, no. I'm not just a product of everything I've ever read over decades of life. In fact, my choice of reading has been largely a "product" of my own interests and lifestyle and stage of life.
As someone else said, who/what I am (as someone who writes) is a product of all kinds of things in life, including personal experiences and interests. Also, as with many women who have lived long enough to have had a number of close relationships/friendships/conversations with other people; much of what goes into what I know (when I'm writing about what I know) has been being there as a friend or relative goes through their own experience of one kind of another. There's much to be learned from long conversations with friends and/or other women; and as the decades pass there are more experiences of our own, but also of those we have those conversations with. Or, there just may be more people that we meet on those terms.
Having said all that, I do think that having been a girl at the time when I was, and reading only fiction about real-life people (for example, not science-fiction or fantasy, for the most part); I grew up to have the complete lack of "frame-of-reference" for anything other "people stories" (of one era or another, but "realistic-people stories" nonetheless). I may be able to appreciate and sit through the occasional sci-fi type of thing/fantasy type of thing, but I have no patience for reading it and truly no "image/vocabulary mental-inventory" to even think about writing that kind of stuff.
So that goes back to the thing that (at least for me) who/what I am as a writer and person has always dictated what I read or write on my own time - not the other way around.