According to Blizzard interviews, the Blood Elves in the Midnight cinematic look different because they wanted to convey "human emotions" which is supposedly difficult to do when your characters have full glowing eyes. I think that's bullshit personnally because while I'm not a 3D animator, I think you can convey expression just fine with facial expression, eyebrow movements and the shape of the eyes, much like they did the much prettier Blood Elf chick in Burning Crusade cinematic.
Now granted, that was a priestess in TBC and Liadrin is a paladin, so I suppose you can expect the paladin woman to look a little more rough around the edges, but the character in-game looks just like any other Blood Elf chick so the difference looks jarring.
But really, of course, they're just trying to cover the fact they made her look more manly because they want to deconstruct male gaze or some such bullshit.
Beside being not nearly as epic as some of the previous cinematics (Wrath of course, but even WoD or BFA felt a lot more epic), this cinematic has several big narrative issues that, to my knowledge, haven't happened before in Blizzard cinematics history, which is both sad and hilarious.
First, very few people would have even known this was Lady Liadrin if she wasn't called by name, because as I said she looks nothing like the character in-game (different armor than we're used to, though that's reflected in her new in-game model for Midnight, different facial structure). That's always an issue when even players who've played your game for sometimes 20+ years can't recognize the main character in your cinematic.
Second, the cinematic's story itself is presented in such a way that most people didn't realize who was coming in to help the Blood Elves at the end. Because they showed them with human silhouettes, most people assumed it was the Arathi Empire that came through because that's the new faction coming out of nowhere in TWW and they have this affiliation with the Light apparently, but nope, Blizzard had to confirm in interviews this is the Army of the Light. You know, the faction from Legion's Argus campaign back in 2018? The one that's basically 90% Lightforged Draenei who are like 7' tall next to Liadrin's 5'5? The faction who has a goddamn Lightforged DREADLORD fighting for them? The faction that wears armor that glows with the Light?
Let's show that? Maybe showcase a few of those characters coming out of the Sunwell... portal, I guess?
Naaaaahhhh.
Instead let's go with generic humans in generic plate armor, that's gonna do the trick right?
When you make a cinematic and most players don't know who is in it and who is coming in clutch to help them, you know you're amazing at your job.
At least Lor'themar looked good (no homo).