Documentation is information intended for humans to understand complex topics. Code is information intended for machines to understand complex topics. Code makes shitty documentation. Code is time-consuming, error-prone, nit-picky, and extremely verbose compared to the kinds of tools designed for humans: WISYWIG editors, buttons, windows, graphics, diagrams, audio, video.
Developers today have grown up in a world where doing anything requires writing code. They literally do not understand how to solve problems without writing code. And have even fooled themselves into thinking that writing code is a superior way for humans to solve a problem than clicking a button. So rather than have robust tools that solve our problems, we now only make tools that require us to create our own customized tools to solve our problems. Forever making slapped-together jigs for every project, rather than just buying and using a premade tool.
Confluence is what a documentation-creating solution should be. Not only does it have a WYSIWYG editor, it has custom plugins, rich content, and dynamic components, all of which can be added anywhere, immediately, with a live preview, with no training, no code, no syntax. Simply an interface for an average human to make a beautiful, useful document, quickly and easily.
From their page: "I like Markdoc because it lets us still do anything we want with code in the docs without bogging down the content authoring experience. If we need some new component, designers and engineers can whip that up. So as a writer, I can work in the docs content and stay focused."
You can do the same thing with Confluence. They just had Not-Invented-Here syndrome, and wanted to do something with their excess engineers.