They simply announced the wrong races. Here, I'll fix it.
Alliance: High Elves, Wildhammer Dwarves.
Horde: Zandalari Trolls, Man'ari Eredar.
Neutral: Nightborne, Highmountain Tauren.
The Sunwell is destroyed. The orcs make nice with a group of eredar (They know what it's like to be rejected by the legion and then other mortal races) who use their knowledge of the Fel to restore the Sunwell with the souls of the leftover Legion-loyal demons. It now glows green. This pisses off Lady Liadrin, who shuns the fel, and takes a bunch of other unhappy self-righteous light-crazed Blood Elves and brings them to the Alliance, where they find refuge in Dalaran, Suramar, and the Vindicaar.
New customization options: Lightforged stuff for draenei and High Elves. Fel customization for Blood Elves and Man'ari. Tauren, Trolls, Dwarves, and Night Elves all get new customizations of their own, to reinforce their own race's fantasies against the newcomers.
Class combinations: Nightborne druids are a thing, because some of them allied with the Night Elves, which plays nicely into the neutral Night Elf and Tauren "subraces". Wildhammer Druids even out Zandalari Paladins *and* Horde Druids; both Zandalari and Wildhammer can be any class except Demon Hunter, and maybe Warlock. High Elves can't be Demon Hunters, Death Knights, or Warlocks, but the rest of their classes mirror their Blood Elven counterparts. Man'ari lose Death Knights, Paladins, and Shaman, gain Warlocks. Maybe they could work in Man'ari and High Elf Death Knights, but they'd need to lack the fel-corrupted and lightforged customization options.
I like symmetry, mmkay