it's pretty basic topology - embedding versus immersion. you cannot embed anything but the simplest software in a 2d plane. you end up having to endlessly try to structure things to minimize line crossings, make multiple diagrams of the same code to capture different aspects of it, or otherwise perform perversions just so it fits on a page.
And I live through this. most of my early career was DoD related in the early '90s, when things like functional analysis was all the rage. endless pages of circles and lines which were more confusing than helpful, and certainly didn't actually capture what the software had to do. Bever again.
I agree with you how-ever the elephant in the room is a image or topology doesn't predicate anything (A predicate is seen as a property that a subject has or is characterized by). That is the main delineation between them, and why SPO (subject predicate object) is used universality by all modern languages - abet some have different svo ordering but I digress.
The next major draw-back with visual programming is they don't explicitly convey time. You have to infer it via lines or sequence of diagram blocks. Were in a programming language you have sequential order of execution eg. left to right, top to down of of the program flow and stage change. If you attempt to achieve the same with a stateless event driven bus or message queue, you end up having to embed the sequential control flow into the event payload itself.
And I live through this. most of my early career was DoD related in the early '90s, when things like functional analysis was all the rage. endless pages of circles and lines which were more confusing than helpful, and certainly didn't actually capture what the software had to do. Bever again.