Only because they were so bad at it.
I personally would have been fine with them dropping the factions and having us join up to face larger threats after Legion. Throwing BFA in there then wanting everyone to just forget about it just absolutely destroyed any and all verisimilitude WoW had left, reducing the characters and the narrative to the level of a Saturday morning kids cartoon.
I understand that sub numbers require the removal of the faction system for the survival of the game. Just wish they would have thought about that before they started having one of the factions committing war crimes against the other. You can’t just sweep that narrative under the rug.