Man pages are not tutorials. They are not help pages. They are reference material, designed to quickly and briefly inform the experienced user about the usage of a command and any related files.
Info pages are the next step up. They are often more detailed (witness the Emacs pages) but they are generally written for a technical audience and quite frankly, the average user isn't going to find them anyway or be able to do anything with them if they can find them,
Man pages and Info pages will, if you are very very lucky, be written by the authors of the software who speak the same language you do and are used to writing technical information. They stand some chance of being updated as the software is updated.
Next up on the list of information resources is wikis, hosted at the site where the development is done. These will generally provide more accessible information for new users, will be community driven and hopefully will reflect the state of the code in the last two years. Keeping wikis up to date is a huge task for large projects.
Beyond that, proper documentation requires constant community involvement. Most projects don't have someone looking after the docs - the software is the focus. Even teams like GNOME and KDE struggle to keep their docs even vaguely up to date - witness the dearth of information on the latest release of gdm (2.28.1) for example. And these teams do have volunteers who are trying to keep up with the changes.
Forums actually give the best location for problem solving because they quickly acquire a list of problem reports that are the things that 90% of people hit. These show up clearly in google and will, hopefully, get solutions posted or FAQs written.
Until the non-technical users of Free software step up to volunteer to write and maintain documentation for software projects, there will always be a lack of current, complete and easily accessible documentation. However, good documentation is hard to write and I often find that commercial software projects are distinctly lacking when it comes to good writing, so I don't think this is an issue which is restricted to open source software.