Good question, Tracy.
At least since I was in my mid-20s I’ve known that some other people — visual artists, filmmakers etc — have a much better visual imagination than I have. Until recently, however, I assumed that the difference was quantitive rather than qualitative and that their imaginative faculties were so much better than mine because they’d worked hard to develop them, whereas I hadn’t. I believed that, while they work with and produce images, I work in a completely different medium: words. I’ve tended to see writing as a process of trying to find new and striking ways to put words and phrases together and very much not as an attempt to evoke pictures in the reader’s mind!
In one way, I’m glad I didn’t know about aphantasia twenty or thirty years ago, because I might have concluded that it disqualified me from being a writer, as I was missing some of the essential tools. Now, for better or worse, I’m set on this path and I’m content to remain on it.
All writers, artists, people who make things, have limitations. Mine is quite fundamental, but I’m happy to accept that. I’m pleased that, at last, I know what this particular limitation is.