Blizzard have gone too far down this path now that not much can be done to rectify, but I believe Void Elves and Lightforged Draenei were a massive misstep.
To introduce races who focus so heavily on a theme has a huge impact on your class choice. These two races in particular blur the lines between race and class in my opinion.
LFD cannot be warlocks because of their affinity to the light and yet, because they are given the priest option they are allowed to be a shadow priest which completely contradicts their way of life.
Likewise a VE has dedicated their life to the all consuming void and yet they can choose to weild the light to heal their allies…
Not to mention these two races existing within the same faction. Surely they would despise one another. Given how opposing these two forces are they would not agree with one another’s beliefs in the slightest.
In light of the new customisation options on the Alpha, which are fantastic but should really have have been done years ago. it makes you realise that the vast majority of these ‘Allied Races’ should have just been customisation options in the first place.
What should have happened -
Lightforged skins and tattoos should have been a customisation option added to the existing Draenei, and the alliance should have been given something more unique, such as the Krokuul perhaps? The LFD racials are lackluster as is and the original Draenei racials fit thematically if you decide to choose a Lightforged skin option.
Void Elves were added as a band aid to the ongoing request for High Elves. Why Blizzard will not give in fully is beyond me. They should have just chosen to implement the Silver Covenant instead of these Void Elves.
All they had to do was suggest that Alleria and Vareesa rounded them up to join the Alliance for BFA. Instead they completely made up a race out of nowhere…
This way the high elves could play Paladins or Shadow Priests without much contradiction, and the Draenei could also play Shadow Priests or Death Knights without feeling quite so awkward.
TL;DR
There’s an argument to say most of the Allied Races should just exist as customisation options but I think the two biggest offenders are the LFD & VE’s.
Thier racial themes are too similar to that of a specific class. Existing Draenei and High Elves are more ‘neutral’.