The author notes that their website is a result of static generation, while EmDash needs a server beside an HTTP server and a bunch of static files.

It's partly a fair point. Anything that does not dynamically change with each reload should be generated a a static file, and served as such. When the backing data change via the admin interface, then the page should re-generate. I suppose it's the proper caching approach, and I assume any sane CMS does this now (yes, even Wordpress).

But what a static site cannot do is user-specific content. And EmDash has a elaborate structure of user access levels, various auth methods, etc. Once you have to have a user session, there's no way around having an application that handles this. The simplest example is having a comments section.

You can use page fragments to get close enough. I hacked this together in Varnish with custom headers handled by the backend before it was an actual feature. A bit of a pain but eminently doable, even years ago