Very simple, there is a unique mount available only in mraid last boss, the best (maximum ilvl items there as well), you cannot participate inthat content without addons.
Hence the playing field is not leveled, which means competition is rigged (because you cannot participate in it without third party lua programs and hope to complete it at all, because those encounters designed with those lua programs in mind).
Hence a large proportion (95%) of players base cannot participate (compete) with the remaining “elites”.
Which leads to elites being at the same time very selective on who they are playing with,
if you didnt know t here is a dedicated portals collecting log about your performance, which are mandatory to share when you “apply” (Jesus) to guilds.