But program code is 2D as well. And quite limited 2D, with 80 characters width max (or similar, but never unlimited).
Visual languages trade named links for global wiring, which is very cluttered for serious problem solving.
Another way to think of it is "there is semantic meaning to 'the character to the right/left of this one', but is there to 'the character above/below this one'?" In most programming languages, there isn't at all.
Existing visual programming langs can definitely do "named links". A lot support named function-like blocks which are another form of avoiding wires.
> which is very cluttered for serious problem solving
This clutter is also problematic in textual programming, and is the reason abstractions and programming structures are used. Perhaps the hint here is that we need better ways of representing abstraction in visual programming.
At any rate it's (mostly+) categorically different from what visual programming attempts. Code must be read, comprehended, and a mental model built. Visual programming is designed to give a gestalt spatial intuition for code structure -- a different kind of comprehension.
+Indent and spacing between functions/methods does count as a tiny bit of visual programming IMO