The problem with "a single model of everything" is that it is an inferior tool.
It's a drawing or diagramming tool, but the stand-alone diagramming tools are better.
It's a text composition tool, but word processors are better.
It's a code writing tool, but IDEs are better.
In every single thing it tries to do, a specialized tool is better. So this single tool needs to be close enough to the best in every category in order to not be a boat anchor holding you back. So far, nothing has come close.
Nothing stops us from using specialized tools in this case. They just need to not work on "single source of truth" of their respected domain, but on a projection of a single artifact into relevant dimension. Devil's in the details, of course, but at least with IDEs I can tell with certainty, based on my experience, that sticking to editing directly the single source of truth plaintext codebase is wasting much more time and cognitive effort than IDEs are saving us.
Yes, that is good point. It might be reason why it fails in practice. Whatever view one produces from a single model, it will look crappy and cheap compared to the Powerpoint slide of someone else. It might be more truthful and more up to date, but it isn't as persuasive. Persuasion is what a presentation is ultimately about: It should influence the behavior of the audience.
It's a drawing or diagramming tool, but the stand-alone diagramming tools are better.
It's a text composition tool, but word processors are better.
It's a code writing tool, but IDEs are better.
In every single thing it tries to do, a specialized tool is better. So this single tool needs to be close enough to the best in every category in order to not be a boat anchor holding you back. So far, nothing has come close.