> The fundamental issue here seems to be that there's a select group of "Wikipedians" who are the primary editors.

It's actually not clear that's true when it comes to primary writers. There are a group of active editors (about 3000 at any given time) who do much of the maintenance work, e.g. putting articles into categories, formatting references, editing for style, moving stuff around, adding infoboxes, etc. But at least one study (I'll see if I can dig it up) found that a surprising percentage of the total content on Wikipedia is written by random anonymous IP addresses that show up to write a few paragraphs on a subject and are then never seen again.