The minimalist style of both this writer and me does not sell the concept very hard. But you could attain any look you want, however fancy, just by pasting two lines in the head of each of your static pages: a stylesheet and a script tag.
Nunjucks is cool, but now your website is no longer static. You need to run every page request through Node. That's not too bad, but I took the loss of nav as the better road.
However, if you really want consistent elements on every page, you could probably do the job with m4 and a makefile. You can party like it's 1998.
No clue if anybody still does this, but it worked great in 2001.