I should start by saying that I’m one of those people who doesn’t PVP. I don’t enjoy it, and I also suck at it. (Maybe if I liked it more, I’d suck at it less—or maybe if I sucked at it less, I’d like it more.) But that probably doesn’t really matter when you’re talking about story and NPCs anyway. For whatever it’s worth, here’s my honest take, and I make no claims to speak for anyone but myself here:
I don’t enjoy fighting against Alliance commanders whose primary motive for fighting me is revenge for suffering that they have gone through at the hands of the Horde, particularly the modern Horde. Once upon a time, I could have felt okay about being against an Admiral Rodgers or a Leyara—back in the day when it genuinely seemed to be a cycle of hatred fed by both sides—but the whole Jaina fiasco has completely drained me of the ability to be enthusiastic about it.
This isn’t just theory. I know this from my experience with the Battle for Lordaeron at the beginning of BfA. If I couldn’t enjoy defending Undercity from invasion because of the constant drumbeat of “We deserve this” in my head, then I don’t see how this would be any different. That was also framed as protecting something precious to us, something that we would objectively see as worth defending, but it fell flat. I don’t know how the game could make me feel more investment in throwaway NPC civilians than in a place where I did some of my early questing and that I still visited every Hallow’s End.
I fear this is an insurmountable problem, because I know that the entire goal of the Alliance-side scenario is to provide the sense of getting revenge for past wrongs that the PVE storyline didn’t give you.
I give you credit for making a genuine effort to make both sides happy. If this scenario had appeared several expansions ago, before things went so sour, it might even have worked for both sides. It could have been a fine battleground story circa MoP; it might even have worked in Legion. But I don’t think it can work for Horde players who are invested in the story right now, after BfA, with the state the story is currently in.
And maybe it doesn’t have to? I’m sure there are lots of Horde players who would just put on their red shirts and go fight Team Blue because they find it fun—enough to provide satisfying opposition to the Alliance PVPers who are in it for the story. Maybe just writing the story for them is the best you can do.