First: Void elves are no longer interested in "who" they used to be, by just reading the main quest to unlock the void elves in the first place. They never go melancholic, about "How i miss being a High Elf", or anything like that. They are proud of what they are now, and their new alliance.
Second: If i take a guy from Texas and give him a rat + mutagen and suddenly he turn into Splinter, he longer identify himself as a human, maybe he was a human, but not anymore. So he use his new skills and what he learns to become a new character. And just like that....Nightborne doesnt identify themselves as Kal'dorei. Or Dark Iron Dwarves as Regular Dwarves. Or even a Mechagnome vs a Gnome. They become a New society.
Another example of this: An Altmer doesnt think a Bosmer or a Dunmer is his culture or family. They even dislike Dunmer a lot, since they are normally their enemies. A Orsimer dislike all the other races a lot, but have a different culture than the other 3 mer races. The Orsimer serve the empire most of the time and go to war with them, against their old cousins, the Aldmeri Dominion.
So, in games, things are represented like this. One race is not related at all in terms of culture and political views. They become things apart, like is being represented in all of that text walls in the pages of wowpedia or other lore sources of WoW.
And Finally, Actually, you and Blizzard are wrong. You, for thinking that's the framework and for Blizzard, for not respecting the work of their Lore Masters, and making clear mistakes by delivering the product to the player base. And no....I dont admit to that point. One reason i love Elder Scrolls Online, is that they dont shot in their own shoe. Blizzard does. And i dislike Shadowlands a lot, because of that....
The framework was broken since when....Warlords of Draenor?. Legion?. At least in MOP they created a complete line of lore for the Pandaren, since they always had been a mystery of why they even existed.
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Taken from:
https://wowpedia.fandom.com/wiki/Hig...g_of_the_elves.
Splintering of the elves
The surviving elves were somewhat scattered, until Kael'thas Sunstrider, son of the deceased Anasterian, began to organize them by reclaiming every elf he could find and joining with Lor'themar Theron, who had done the same in Quel'Thalas. Under Kael's leadership, they took the name blood elves, to remember the death of their king and brethren. About 90% of all surviving high elves became blood elves.[2]
The blood elves fought to reclaim a small portion of Silvermoon, but most of the city and their land, in general, was haunted and overrun by lingering undead, while their buildings remained in ruins and vengeful Amani trolls began striking out again.[9] Around 15% of the newly-named sin'dorei, led by Kael'thas himself, started traveling throughout the land in order to find more surviving elves and to find a source of magic to replace the Sunwell. The elves were suffering from great withdrawals after being cut off the Sunwell because of its destruction. Due to the unreasonable orders of the Alliance leader Garithos, Kael's people were forced to ally themselves with the Naga and fled to Outland. They soon joined Illidan there, and he, in turn, taught them how to sate their hunger for magic by feeding on alternative sources (having himself suffered the same withdrawal for thousands of years). Kael's blood elves began to hunt and use demons in order to steal their powers, although Kael's alliance with Illidan (and worse, his new reliance on fel magic) was kept a secret from most of his brethren back home.
Most of the remaining "high" elves had chosen to remain with the Alliance following the Second War and did not return to their kingdom following the Third.[7] When Grand Magister Rommath returned to Quel'Thalas to teach them Kael's magic siphoning ways, some elves were disgusted by the practice — likening it to vampiric behavior — and opposed its use. Unable to lead a divided nation, Regent Lord Lor'themar exiled the dissenters from the kingdom, the exiles finding residence in Quel'Lithien.[11]
The blood elves who did not travel with Kael'thas to Outland remained behind in Quel'Thalas and reclaimed much of their land from the Scourge. They eventually allied themselves with the Horde through their connections to the Banshee Queen Sylvanas Windrunner, now the leader of the Forsaken. Although the blood elves harbor very little trust for the Horde, no one else was willing to fight for Quel'Thalas at all.[8][11] Their relationship with their ancestor race the night elves is not flourishing, but they are not dire enemies either, as distance between their locations has meant less contact between each other and fewer situations to arise that would cause fighting.
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Read the damn lore dudes. Is just right there.