I’ll be honest, I think the writers really want to step away from the factions generally, and are just looking for methods of removing characters that they no longer feel have a place in the lore or just don’t want to write about for a bit.
I get where you are coming from with Dragonflight, and a slight vindictive part of me is saying “Hey, this is basically the Alliance story from Battle for Azeroth, where we just watched the Horde have all the story and plot. And then again when the Horde got the Undercity back in Shadowlands.” But that’s not a particularly helpful opinion, and more of a gut reaction. I think the new world tree and retaking of Gilneas is just a sneaky way of writing out and wrapping up the stories of Tyrande, Malfurion and Genn for the foreseeable future.
In truth, I think the current writers, who seem to be mostly new to the team, with a lot of the old writers and leadership having left, in some cases for very good reasons, really just want to write one story that is very… modern. And when I say modern, I just mean they want the story to be more focused on notions of personal growth of certain characters and write themes that just feel that they fit more so in a more modern setting.
I don’t think the stories they write are always terrible or in the wrong places, but there’s a clear inconsistency with writing depth, forgetting or even being quite scornful towards older characters and lore and really just making their own World of Warcraft story. It is kinda like the Disney thing with Star Wars, where they seem to actively want to mock, degrade or just use old content to draw people in, but then push quite often sub-par new stuff, though I guess that’s a matter of opinion.
Under the old guard, and I am glad they are gone given their, let’s just call it misdeeds, there was a certain sense of continuity, where characters acted largely the same way they had done before, and would have character growth moments, but these were generally a little slower and felt more genuine. Nowadays, everyone is quick to kiss and make up and forgot quite frankly the horrible things both factions have done to each other. Is this a positive thing for these characters and factions? Yes. Does it make sense narratively? Rarely.
Sorry, I went on a bit of a ramble there, but I think ultimately, the writers are just catching up with old plot points and writing out old characters so they can focus on the ones they like more and make them more narratively relevant. If there were more Horde characters with unfinished plots around, likely we’d see more of them being discreetly written out.