There was a brief time before platforms took over that data seemed as though it was first class and would break free of any presentation or shackles.

We almost had a P2P semantic web. (Web 3.0)

Not really a lie, if your browser has the "reader mode" button.

Back then it was more about getting people to use CSS better (learn about it) and to use separate files (use classes not inline styles).

Back then, pages were rendered on the server and in many cases there wasn't much templating either. People would normally have their sql query code, their business logic, and the html in the same function in a file >5k lines long.

Bsck then it made perfect sense. Now, considering everything else that's going on in Web development (JS explosion), perhaps not so much.