I know there are some differing opinions on the Nightfallen not being accurate to their NPC models in Legion, and the Highmountain Tauren are just Tauren-with-antlers, but I would still consider them generally strong additions (I hope the Tauren -- Bloodhoof and Highmountain alike -- get some time to shine in the story at some point).
Meanwhile, the Alliance has Dark Iron Dwarves -- which, I think we can all agree, are pretty fucking metal and awesome -- and then... the rest are shit.
Void Elves - Visually, they're "another race of PURPLE elves", except "edgy". In terms of lore, they're such an ass-pull there's simply no choice BUT to ignore them. They will never be important in the game's Lore, ever, because their introduction came out of nowhere, and to nowhere they have returned. "Void" elves, indeed...
Lightforged Draenei - My real problem with this race is that, by the game's own lore, they are presented as being "BETTER Draenei" than the existing Draenei. It would've been better if they'd been a genuine racial-offshoot, that "these are Draenei that spent tens of thousands of years fighting the Legion, where the only physical source of light was literally the Naaru". Visually, I'm okay with them (other than the armor and "jewel" on their tail doesn't match the rest of their visual cues), but they're a rare instance of a "new" race that, simply by EXISTING, makes one of the old races seem worse (because if your Draenei was TRULY powerful, they would become Lightforged, barring some mental gymnastics to justify them NOT wanting to become "powered-up").
Kul Tirans - Fat humans. To be fair, they *almost* look cool, they're just TOO large and goofy-looking, to the point they almost look like they were stylized completely differently than other humans. Players have been asking for Vrykul ever since Wrath; the Vrykul should've been the Allied Race in the Kul Tiran's stead.
Mechagnomes - Are you fucking shitting me? The new character-models for Gnomes already made them the unambiguously UGLIEST race in the game, and now you're going to double-down on that? Oh, and their culture is EXACTLY the same as the tinkerers of Gnomeregan, they just have a shitload of amputees running around. Those are cool options, for sure, but in no way, shape, or form do they justify being a separate fucking RACE. Nothing about them is even vaguely distinct from "regular Gnomes", they just have some snazzier options and built-in goggles.
The Allied Races the Alliance *SHOULD* have gotten:
Vrykul - 'Nuff said. Just explain them as a clan that was lost at sea, and only recently came back to land (perhaps related to the disturbances of their 'gods' during the events of Legion).
"The Broken" Draenei - Ugly, but also VERY different from existing Draenei. Would make both races seem cooler by comparison. Could also enable wildly different class choices (no Priest or Paladin, but perhaps adding Warlock and Rogue).
PLOT-TWIST - Highmountain Tauren!!! Instead of "Void Elves", I think it would've been far more appropriate to have added the Highmountain Tauren. As outsiders looking in, they would've been the perfect parallel to the Nightborne. Looking at the Horde and Alliance (in their CURRENT state) objectively, I feel like the Highmountain would've probably been more inclined to join the Alliance. Failing that, I think "High Elves" would've been fine, provided they drew more inspiration from Alleria, being a bit more "rugged" and sporting tattoos or war-paint.
Mindflayers or whatever-the-fuck they're called in WoW - Basically, the dudes with the tentacle-faces. They're clearly based on the Forsaken models. I'd probably make them stand upright (more "fancy" looking), still thin but more evenly-distributed, scaling down the size of their heads in proportion with the rest of their bodies.
I mean, it's far too late for any of this input to be important now. But, much like the storytelling, the Allied Races for the Alliance have been completely boring and unimaginative. And given it's still looking quite likely the Vulpera will be joing the Horde, the prospect of fucking "Mechagnomes" for the Alliance is borderline insulting.