The only time I've seen visual programming work is when the state is immutable. How-ever it requires a major paradigm shift how one design, develop and test their programs.
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.
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.