Visualizing large graphs is a "tarpit idea," one that initially seems appealing but never succeeds in practice.
Fundamentally, the problem is that visual aids can only really represent a few dozen things before they become as complicated as the thing you were trying to understand in the first place.
And when analyzing messy node diagrams, it’s not just the nodes we’re trying to visualize, but the lines connecting the nodes (the “edges”). We can only visualize a few dozen of those, and that typically means we can visualize only a handful of nodes at a time.
Visualization only works in trivial examples where you don’t need it; it fails in complex environments where you need it the most.
This is my problem with node based editors, the one I am most familiar with being blenders shader editor. I mean, sure, I guess it represents the internal structure. But it always feels so messy. Sometimes I wish blender would just let me work with a netlist.
There's a threshold, of both user ability and scale of 'problem'
I mostly agree with you dfabulich - the repeated efforts to create node/pipeline tools "visual programming languages" are not built for us, and feel redundant.
But I took issue with "where you don't need it" as this is very much dependent on who "you" is.
I would go further. The fundamental problem is the idea that there is a fundamentally correct representation of something. This actually goes further than even the visualization of the graph. Symbolic representations have the same trap.