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Their external links policy on "open wikis" dictates wikis must have "a substantial history of stability and a substantial number of editors." I saw the 100 editors figure mentioned but there is no basis for that in policy. It is also beyond folly to judge a wiki solely by the amount of active contributors. Our editor count is a weak argument from their side.
I'd say your best bet is to demonstrate how we have a "substantial history of stability." I don't know what would sway them, but perhaps it is worth pointing out how long this wiki has been operational, links to our site from the media (perhaps in relation to Stranger Things, Baldur's Gate III), or that one tweet where Ed Greenwood sent readers to our wiki, something along those lines.
Ultimately we are not affiliated with Wikipedia in any way nor do we benefit greatly from being linked to by them (as far as I am aware). If they want to rob their readers of a valuable resource it is their own call.