I like the simplicity, but does everyone actually log in to the server and edit the files directly in the same repo, or is the repo exposed over SSH and everyone works in forks on their own machines?

The first one doesn't really scale beyond a handful of people, since you risk losing work if the same file is being worked on by multiple people. Vim shouting at you that the file you're editing has changed on disk is not good enough.

I can see how this could work with a central repo, though. It does require everyone aligning on the same conventions and workflow, so you likely still need some software to ensure this is done correctly.