I have aphantasia, and I’m a writer. Not a professional one, but I do write here on Medium and have written a lot of fiction in the past. Strangely, I never felt inhibited by the lack of mental imagery. It’s hard to describe my process because I don’t really know what it is I’m missing, but basically my brain works in abstract concepts and knowledge, so it’s not all that different from just thinking purely in words. I just write down the words I come up with.
In a way, lacking a visual mind could be seen as a benefit to writing, not a handicap. Since I don’t have to first translate from image to words, it’s like I’m already speaking the native language of a reader. There’s less chance of misinterpretation.