I've come to realize that the term "didactic fiction" has negative connotations. The more I look for it, the more I encounter it in the context of someone defending a piece of fiction by saying... "it wasn't didactic at all." In that sense, "didactic" is taken to imply something "preachy" and annoying, something that ultimately distracts from the main function of fiction, which is to entertain. Imagine a novel written with a strong Global Warming theme or some other controversial theme and the main character is a scientist who fights to get politicians to listen to him. The story could easily turn very preachy and "didactic". If the main objective of that novel is to entertain, but use a theme likely to get some traction, then it makes sense to stir away from something too "didactic."
I could try to avoid using the term, just to steer away from the negative connotation but to be perfectly honest, there is a strong didactic element to what I am writing and I am not comfortable pretending otherwise. My task is to explain how a piece of fiction can be didactic in a good way and sufficiently entertaining to keep the reader's attention.