Your blog post may be beautifully styled, but that makes no difference if I can't even load it, or the fonts are so thin I have to squint to try to read, or the glaring white background makes me see floaters. A blind person doesn't care about the whizz-bang of $framework if your JS-only site breaks their screen reader.
For other use-cases... that's why we have HTML and stylesheets. The problem has been solved, mostly sort-of.
As already mentioned, this is demonstrably false. I'm choosing to give you the benefit of the doubt and assume you don't understand how a great amount serious media is served nowadays, since the alternative means you are attempting to score internet points with a second-level contrarian post. But I have to wonder where you've been.
The separation of structure and formatting is not practical for serious advertising platform of any kind.
The separation of structure and formatting is not practical for serious media of any kind. You can't separate form and content. Nor would most people want to, because (visual and other) complexity is an inevitable and rewarding part of human experience...