As someone without aphantasia, I don’t always quite get it either. Reading is often a last resort medium for me, but it does have it’s place. Plain text primarily engages my narrative imagination (where is the story going) and only a little bit of visual imagination (since it’s kind of hard to convey certain things like body language in text without being very boring), while for example a video might invoke narrative, visual, and auditory imagination. Video games are even better to me, as they engage narrative, visual, auditory, and decision making imagination. It’s about stimulation to me, the more coherent the better, and books just don’t seem to stimulate enough for my imagination to kick off to where it’s enjoyable to read.