Absolutes like this contribute significantly, depending on the perspective they're spoken from, to the anti-intellectualism in our society today, or to a culture of elitism.
For the first, some things are complex, and that complexity is part of the real-life systems and structures they have to interface with or represent. Explaining complex things with a diagram can be an extremely effective method for making what might otherwise require a very high cognitive load much easier to process.
And for the second, if someone needs a diagram to understand something complex, it's not because they're stupid, and insisting that everything worth explaining can—and must—be explained in text only does them a disservice.
It wasn't meant to be an absolute, it is just a rule of thumb, and for me. I expressed it that way for rhetorical purposes.
I don't think retreating to real language is anti-intellectual; but you may be right that it's elitist to mistrust stories told in pictures. Anti-intellectuals mistrust stories told in words.
By contrast, WiX# provides a complete code sample that specifies a complete installer in less than 20 lines, with no diagram necessary: https://github.com/oleg-shilo/wixsharp
I...do not feel that this follows in any way, either as an absolute or as a rule of thumb.
Usage of WiX-sharp (which wraps and hides the mess decribed above) is so simple that a complete sample project is just a few lines of code, as shown in the README. There is no diagram because none is needed.
This is consistent with (but doesn't prove as a general rule) the idea that "if something is so complicated it can only be understood with a picture, it's too complicated"
Ticket management is stuff that needs doing, obviously.
Diagrams are illustrations; if something is so complicated it can only be understood with a picture, it's too complicated. But a quick diagram on a whiteboard (or with a pencil on the back of a fag packet) might be helpful.
Presentations (with slide-decks) are for managers[0], not engineers. They are a huge drain on time. I got severely dinged by my manager for doing a presentation without a slide-deck; I hadn't prepared one, because I had real work to do. But I think I showed my manager up, because all the other engineers had turned up with slide decks.
A crap slide deck is quick to make, and completely useless. A really good slide deck can take days to make; it's a specialist trade, like making good user documentation. Slides must augment the presentation, not distract from it.
[0] I've been forced into formal management once or twice; my experience was that at least half of management is bragging to other managers about how important your team is, and slide decks are great for that.