I know you're just font as an example, but doesn't your markdown editor also shove a font in your face? You can adjust default behavior in Word just as well as in another editor.
Anyway, to work within your analogy, I would say that Word lets the write do a bit of a 'mockup' of the set with nearly 0 effort. Like "I want a table here", so 2-3 clicks and you have it. Then you can "let the director" take your mock up and flesh it out properly later. As a writing, it helps me to see the mock up of the product as a go, but I want that mock up to be effortless. And as I said above, I do some work up front to make sure that Word's mock up looks good (or good enough).
...and that's the problem. You can easily get distracted by the look of the words on the page. Is the heading big enough, centered, got enough white space around it. By the time you've faffed about with that, I'm onto my second or third paragraph of content.
Obviously everything that puts text on a screen puts a font in the user's face. But Word also presents you with styles, which make what you see changeable from the whitespace on up. Not only can one paragraph look different than the next, one word in a paragraph can look different from the word following it.
It's true that many document elements, such as tables, are easy to create in Word. This puts it over the edge into desktop publishing territory. In itself, that's not especially a bad thing, especially if your target is a printed file or a PDF. That still makes it a publishing tool, not especially a writing tool.
Anyway, to work within your analogy, I would say that Word lets the write do a bit of a 'mockup' of the set with nearly 0 effort. Like "I want a table here", so 2-3 clicks and you have it. Then you can "let the director" take your mock up and flesh it out properly later. As a writing, it helps me to see the mock up of the product as a go, but I want that mock up to be effortless. And as I said above, I do some work up front to make sure that Word's mock up looks good (or good enough).