Ditto agreed on @
KainneAbsolute's premise being good and better than both the SL and the original Chronicle version. When it comes to this bit though, it's not like this was ever reflected in the content. The Bald Man had to spend a whole expansion and multiple overlapping plot devices along with manually hammering the world soul in a place of power to do what N'zoth could do by passively existing in its vicinity and Sarg has stabbed a planet. So it's just an empty hype statement, best not consdiered any more than Outland being a Death Titan (Afrasiabi) or the 'the people we meet in the Shadowlands are gestalt beings of all their possible selves' (Danuser).
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No, this explanation works only if there's actual faction gameplay thing keeping you from doing content with your friends. But it doesn't, because you can do groups, guilds and all instanced content cross-faction. There's no gameplay impetus to force ill-fitting races to join a faction that doesn't make sense for it. The whole thing about the individual choice of every race waters each race down into a useless lump, because if anyone can be anything and the message of the last three fuckmothering expansions is 'Be Lawful Good, hug it out, be nice to everyone, all material, racial or political differences are just the result of bad vibes' and any group can adopt this message then everyone ends up the same. The result of this is the current Horde cast or that end of DF cinematic where all the blandos are so interchangeable they finish each other's sentences. Differentiation is good.