My favorite static site generator is Org mode[1] for Emacs. Org files are written using a feature-rich lightweight markup language[2] that is much more powerful than Markdown (e.g., plain text spreadsheets). Org files can be exported to HTML[3].
The reason I prefer Org for static site generation is not because I already use Emacs. I actually started using Emacs about 20 years ago specifically to use Org mode.