And if Warcraft was not in the video game medium in anyway I would have the same mindset you do. But it’s not and thus presentation is equally important.
I have this mindset because WoW is a video game from a company that makes games for gameplay first and in that context lore presentation will never represent its actual lore.
What you and others have to accept is that there is no such thing as a single unified canon even among the presented material in game. What we have are different stories told or experienced by to different people and those stories will frequently contradict each other.
The War of Thorns is a stark example of this. Alliance and Horde players experience different stories which frequently contradict each other… and I suspect that’s intentional to drive player faction conflict.
Because the central theme and spirit of this game, this very franchise, from the day Orcs Vs.Humans hit the shelves, is that “dumb alliance horde war story”.
Then why did Warcraft 3 involve us working together against a global threat? Every expansion has either started or ended with us working together against a larger evil.
This “central theme” is only relevant for battlegrounds and war mode.
The Battle of Hyjal did not turn into a love fest between Horde and Alliance and if you go back to it, you’ll see that the troops did not fight together, there was a Horde wave, an Alliance wave, and finally the Night Elves and Malfurion in the last act of the Tree itself.
The Alliance/Horde conflict was central to the story of Theramore and major horde characters such as Rexxar, Thrall, as well as Jaina and Daelin.
And it would be the faction conflict that bridges Warcraft 3 and the opening drums of World of Warcrraft.
Every chapter of this game without fail has consistently had new battlegrounds for something the Alliance and Horde would fight over. PVP is an essential element of this game for a large part of the player base, and they’re not going to neglect expanding on it for Shadowlands.
“Just as the orcs, humans, and night elves discarded their old hatreds and stood united against a common foe, so did nature herself rise up to banish the shadow forever…”
Which ended with Jaina allowing her father to be killed in order to have peace.
You’re exaggerating the importance of battlegrounds, where every one past vanilla has had little lore to it.
Pvp for Blizzard has become a side game, as they’ve been neglecting the wishes of the pvp community to return vendors. Pvp endgame also caters towards arenas and the barely used rated battlegrounds, which hardly involves fighting the opposing faction.
I might be remembering wrong but I think Tyrande, Shandris, and a few other night elf units start out in the Alliance base at the beginning of the Hyjal defense level in WC3. But either way the player can use their night elf units to support both the Alliance and Horde bases.
Was there new battlegrounds in Legion? There was the WPvP in Stormheim but I don’t remember a new BG. This is besides the point though because:
in terms of competitive PvP, as has been pointed out, the most popular is the Arenas, which hardly has anything to do with the faction conflict. You fight teams made up of your own faction in the Arena half the time. Even for casual BGs, there is mercenary mode where you can sign up to join the other side.
Seething Shore 10x10
Ashran 40x40 (this was the big mass battle battleground, Legion’s Alteraac Valley) the only other 40x40 battleground in the game.
Arathi Blizzard 15x15
Silithus Brawl 15x15
and some others that didn’t survive the cutting room floor.
Ashran was WoD so idk what you are talking about with that one. I don’t count Arathi Blizzard as “new” because it’s literally just Arathi Basin with snow added to it. It’s a reskin. Seething Shore came with the last patch of Legion in the build up to BfA, the whole thing revolves around Azerite, so it’s more a new BfA BG than Legion.
If we are considering different things canon there’s no real point in trying to have conversations here if we aren’t even talking about the same thing. Might as well just be talking to ourselves.