Is your feature request related to a problem? Please describe.
sphinx.ext.autodoc is used for documenting only python objects, and that is perfectly fine. With the recent refactoring, it is a bit clearer that there is no special sauce in there, one can replicate it for their own domain just by populating the contents appropriately.

The suggestion here for "supporting" non-python documenters is more about providing some documentation and guides for how people can replicate the workflow of sphinx-apidoc -> auto* directives -> domain-specific directives.

• Have a tutorial for such a workflow. We can extend the recipe example and have it parse yaml files as the "auto" part there.
• Have the sphinx.ext.autodoc directives be owned by the python domain so that it would not clash with another domain that could similarly have an automodule (e.g. CMake also has a module entity that could clash there)
• Provide some useful helpers so that users avoid repeating themselves when constructing the content. I am primarily thinking of the context of autodoc: Parser agnostic content build helper #14051 and having a simple way of supporting more arbitrary text formats (both rst and markdown) that the content could have been written in.

Additional context

• Split from Restore the legacy implementation of autodoc for compatibility #14091 (comment)