I don't have aphantasia, I can easily imagine things when I want to, in fact I used to paint, it's just that when I am thinking, or doing any sort of intellectual work, I find visualizations more of a hindrance than helpful.
I also don't have an inner monologue unless I explicitly opt to, which I only very seldom do.
As a side note, I find most diagrams a waste of my time, more often a deterrent to understanding. I have always had great trouble producing diagrams for others, at work.