@Notsonoble
GNU doesn't make good use of the web format, that's true. It's probably intended for print so they can't include fancy menus.
The font is fine to me, but it looks like it chooses your default font for sans-serif. Mine is set to be Inter (would recommend).
I'll give you a more modern documentation which does use the horizontal space nicely while keeping the content at a comfortable width: docs.astro.build/en/concepts/why-astro/
The FreeBSD docs are okay, but they need a way larger line height. A factor of 1.8 is typically considered good at that line width, but it only uses 1.5.