Hmm?
In my experience, that's exactly where Wikipedia often shines: many articles offer quite broad coverage of their subject, approach it from multiple points of view that do a good job of making it accessible for people of many levels of knowledge.
This especially seems to be true of articles on math. Whereas something like mathworld.wolfram.com usually offers a concise, accurate, and well-written article on a subject, it's quite often at a fairly high-level, and may be hard to understand for someone missing some background. The equivalent Wikipedia article on the other hand, is often much longer, because it approaches the topic from many points of view: concise technical explanations suitable for a mathematician, more intuitive (but maybe less rigorous) explanations aimed at a general audience, implementation hints and algorithmic summaries for those interested in using it in a computer application, etc.
This sort of shotgun coverage can result in rambling, lengthy, and sometimes redundant articles (it's usually pretty clear that many different authors have edited it, and the collaboration mechanisms are far from perfect), but I've found it immensely helpful when trying to understand something which is just a bit beyond my level. Seeing the same subject explained from multiple points of view is often just what's needed to make things click.
That's one of the reasons I love Wikipedia... it's not always the most elegant, but it's proved a very practical and helpful resource.