The story is a dozen more steps backward compared to Legion. they just reduced the expansion to a very pointless faction warfare and the way they've written the story just flies in the face of everything.
first of all, Alliance poses no real threat to the Horde and yet Sylvanas pulls a Garrosh and suddently nukes Teldrassil to "secure the future for the horde's children." what future? Teldrassil isn't threatening the future of Horde, Horde already controls a major portion of Kalimdor. Theramore is no longer threatening the horde either. so why nuke Teldrassil and start a war? what purpose does it serve?
Sylvanas is NOT Garrosh, Garrosh's actions were driven by his vision of a true horde with just Orcs in power, he was an idealist and an authoritarian figure. Sylvanas is a survivalist, She might be an amoral character and sometimes even evil. she might be selfish and self centered, but her actions are not driven by a vision of a world free of the living. she is only in it for herself and for her to survive she needs her people and the horde.
I would've LOVED the new expansion if it was based on the theory that Teldrassil needed to be destroyed to save Azeroth, but it appears that this is not the case. think about it, how likable Sylvanas and Horde's story could've been if they were forced to destroy Teldrassil out of neccessity and not out of some pointless vision of a kalimdor controlled by the horde. remember why the Tushui and the Huojin joined seperate factions in the first place? the tushui valued careful thinking and taking the best decision after gathering all the facts and analysing the entire situation while the huojin think that sometimes drastic measures have to be taken before it's too late. now both sides are not wrong in here, and I can see how each individual may root for different factions.
The horde could've burned Teldrassil to save us all while the Alliance side would refuse to go through with it until they have all the evidence and all the facts, but by then there might not have been an Azeroth to save. The Alliance would then see this action not as a heroic move to save Azeroth but as a cowardly attack on innocent lives, this would've added a great deal of depth to how each side perceives and responds to a crisis.
But alas, I think it was too complex for Blizzard writes to make it work, so I guess we're butting heads again over Garrosh 2.0's vision of a "great horde".