I remember as a teenager reading a prolific sci-fi writer who described the technique of not visually describing the MC. So I tried to think about what his characters look like... I knew one was black and one was Chinese because there was a somewhat racist exchange of words between them. Other than that, I had no idea, even for the secondary characters that had been described.
When I first learned about aphantasia it was illuminating, but I realized that I can visualize if I try (and I do dream visually, which I believe is not the case for people with aphantasia).