Its a job. These are hires to create the plot of a themepark skinner box to conjure up excuses to sell another box to keep consumers on the purple treadmill. This is not a labour of love, those people are all long gone, these are people either simply don't care about the past work or have a case of 'now its MY story' which in western studios has been a pretty common thing with sequels nowadays as they pull a The Last Jedi to subvert expectations.
As someone with years of time and money invested its understandable to get upset but at the same time WoWs story is already 'done' in terms of wrapping up the rts's story hooks. But its still profitable. As long as thats the case its always going to have another "N-no THIS is the real big bad that was behind everything and everything before was merely prelude, swer on me mum!" because they need to find a reason to fart out another expansion pack. Thats the state of a game when it outlives its writing. Alt-fic takes over and replaces it with OC's, self inserts and just generic filler because the writers are long gone, the story wrapped up its loose ends and now its just a struggle to find someway to keep you subscribed beyond the natural end to the story.
Its not just a WoW issue mind you but a problem with live service games and persistent worlds in general. Its already been said by the devs that FFXIVs main story has around 3 expansions before it wraps up and if its still making money it will keep getting updates after that but the whole story of a world split into a multiverse and the survivors of the original world trying to cause disasters to rejoin them so their shattered god is rejoined as well has and end and when its done the project will see its leads move on to new games and replacements will do the same Blizzard does now with WoW.
It sucks but no game can last forever before story is replaced by OC churn. There isn't a setting alive that can do it no matter the medium. Star Wars struggled in its novels, Stargate tried to invent a whole new power tier of villains after they wrapped up the story for two more mediocre series of tv and mmos have the same problem too. WoW has just gotten to that point where it feels more like randos being put on a established comic book and they want to make it 'theirs' in ways that dont follow the original creators vision simple because those creators aren't around at the company anymore.
But games are still relatively young enough that longrunning series haven't had to deal with this as much as things like comic books or television. If you have issue with it now but want to stick to a product in its "zombie phase" where its pulling a simpsons and just riding the wave till profitability tanks it aint gonna get better and you are better off finding something else to enjoy to replace it as its not going to return to what you loved. It can't.