But, uh, kinda feels like the author's "reasons" aren't balanced in terms of comparing "maintaining a website by writing HTML directly" to "maintaining a website by using a static-site generator".
e.g.:
"But how can I then keep the style and layout of all my posts and pages in sync?" Simple: don’t! It’s more fun that way. Look at this website: if you read any previous blog post, you’ll notice that they have a different stylesheet. This is because they were written at different times. As such, they’re like time capsules.
...But if someone wanted to maintain/update consistent styles across a website with only HTML files, then this would be a point in favour of a templating system over writing in HTML directly.
Finally, you constantly have to work around the limitations of your static site generator. Let's say you want your site to have a specific directory structure, where pages are sorted under various categories. With Jekyll, this is practically impossible, and even though you technically can get it working if you really try, it is only through much effort and with a source code that is organized much more unintuitively than if you just wrote it directly in HTML.
While it's fair to say that you have to learn the idiosyncracies of a SSG to use it, I'm not sure this is a fair criticism of Jekyll.
Seems that page output is determined by a 'permalink' key. https://jekyllrb.com/docs/permalinks/ (Found through a quick search for "jekyll structure").