[axegon_]

> There are lot's of production codebases with very little or no documentation, though.

Indeed. But the advise is equally as valid for libraries or frameworks used in a project, which as a junior developer, chances are you have very little experience with. Read those :)

> On the other hand, if you are a junior contributor, but can't find the obvious master programmer around, that is a huge red flag that the organization is filled with mediocrity through and through and it probably would be best to work somewhere else.

Also correct. That said, you can go through the history of the project you are working on and see who's done the heavy lifting, granted they are still around.