Automatic layout can work really well if the diagram kind is known. E.g. you don't have that many arbitrary placement options for a flowchart as opposed to an arbitrary diagram. In those cases of your layout algorithm produces an okay result, most people won't miss options to change certain parts of the automatically-laid out diagram. I think I'm that's a major part why solutions like PlantUML, Mermaid, or D2 often require you to specify a diagram type: to restrict the layout to what makes sense for that diagram.

That's a problem that plagues more generic options like Graphviz or (disclaimer: I work on that) yEd where you get the generic layout options and have to adjust them to make sense for your diagram. More flexible, but also more cumbersome, often with the problem that you crave for manual adjustment if the layout is not quite right.