The setup we use is a monolithic MS OneNote notebook stored on MS Sharepoint.
I know this setup is dependent on your shop buying the "expensive MS stuff", but we already had it anyway...
This setup gives us the following "features":
- Everyone can edit at the same time
- Changes are tracked and identifiable by username (you can rewind the file history)
- Editing process is very easy and user friendly (you can drag in files, images etc into your notes, and it just integrates seamlessly. particularly with the rest of the MS Office suite)
- OneNote notebook layout is actually pretty good (horizontal tab based main sections, that can each hold multiple pages of content. these pages can be visually organized in a hierarchy)
- It has good search functionality
To open the notebook and be able to start typing (or pasting in from email etc) is a very low barrier of entry, compared to say using a Confluence wiki page and having to login then click edit.
The last version to work with local storage (not cloud) is Onenote 2016, which is supported until 2025.
We also have a monolithic MS OneNote notebook. The notebook is shared by 30+ people and we haven't experienced scaling issues at that level either.
To add to your list of features, the macOS and iOS apps work well which is nice since we have a mix of Windows and macOS users.
And it also has a very good web version so you can easily browse the documentation even if you are not on your main work computer (from home, from a coleague's desktop or laptop). This is a feature I really on all the time actually.
IMHO MS has really step up their game in terms of the web versions of their apps. A couple of years ago we were still being force fed this clunky outlook web version that only worked properly in IE, and now we have popper functional cross browser web apps for everything.
Screenshot of One Note web interface: