Battle for Darkshore was inadequately handled. There's two major developments for night elves in it that both didn't use pre-existing material, but conjured new bullshit.

Tyrande's Night Warrior nonsense wouldn't have needed to be asspulled, since the night elves have Cenarius on their side. It's nice that they wanted to bring Tyrande to the forefront, but the sudden Sailor Moon power up wasn't necessary for that, and imo it just taints her character and abilities to now just be a vessel of something otherworldly divine (not to mention I personally find her new model uninspired). Such that was barely mentioned in a random Archaeology artefact beforehand. Cenarius is pre-established and very powerful, but not a stable part of kaldorei military, so he'd be a perfect trump card for them to use when things get too rough otherwise. The nuclear option. But no, let's forget he exists and randomly empower a mortal character. Alliance needs more deus ex machinas to their repertoire.

Then the likes of Delaryn and Sira losing faith in shit they've followed for numerous years over something as simple as getting their asses handed to them by a superior fighting force. These are people who fought against the Legion. Night elves losing hope would've been far more credible if Sylvanas had actually shaken something that's integral part of their identity. The best target for that I can think of is Elune; what she actually is has been kept vague. Because of that what evidence of her godhood has been presented could easily be dismissed as smoke screen if Blizzard desired so. That she actually isn't a goddess is something the playerbase has theorised for years and the revelation would be adequate to shake the faith of the night elves to the degree they'd lose hope. Well, that opportunity was missed and if anything the Night Warrior nonsense further cements Elune really is a goddess. A vague, unique goddess of little actual lore to explain her existence.