I think what the author is arguing for is not so much about writing in pure HTML, but the fact the levels of indirections added by most existing site-generating

I think what the author is arguing for is not so much about writing in pure HTML, but the fact the levels of indirections added by most existing site-generating frameworks restricts them from doing something that would have been possible with just pure HTML. This second article seem to argue for owning your own site generator that is a thin wrapper around HTML, to deal with more dynamic content while maintaining flexibility. I have being doing the same for my website since ~20 years ago, where my input is mostly pure HTML, and I generate static HTML pages from those with a few scripts. My website does look rather antiquated, but I consider that a feature.