"Approachable" means that it might require some effort from the reader (eg. in worst case scenario, a reader not familiar at all with the domain would have to look up the definition of every word in a sentence and do that recursively a few steps, until he/she gets some domain familiarity by reading the equivalent of a few hundreds pages or less), but you can approach it, and in exchange it gives precise and rich information!

I like Wikipedia as it is, let's not make it into IdiocracyPedia for the sake of accessibility... if you're not lazy and you're willing to put some focus and time into your research you'll be able to understand quite unfamiliar subjects from Wikipedia, there's nothing blocking you, as opposed to eg. lots of academic articles that may contain un-google-able jargon and unexplained/unmentioned domain specific assumptions.