I don’t disagree with the author, but I found it odd that they didn’t bring up CSS. You’re not going to get something with character like the dolphin man site or Space Jam site just using unstyled HTML.

Not as extreme as this, but I always found it sad that, for the most part, the internet is essentially split between Content Management Systems and content, with the former having full HTML+CSS+JS capabilities and the latter getting barely a fraction of HTML.

The most excellent articles make use of interactive elements, for example:

• https://meltingasphalt.com/interactive/going-critical/
• https://www.redblobgames.com/grids/hexagons/

But even if you don’t go all-out, sometimes a tiny bit of HTML+CSS can help to lay out your article better, or visualize small things in it.
The web has these capabilities, and we’re ignoring them or even barring entry to them.