Making Forsaken scourge-lite in Cataclysm is when her character started getting broken. There were good parts of those zones to be sure, and raising people and allowing them to die again if they don’t want to join is alright enough. But liberally using the blight everywhere, raising enemies and having them inexplicably join the forsaken for nor reason, and other hyper edgy actions tainted the Forsaken and Sylvanas in hindsight. Everything up to that point could be excused as responding to enemy aggression and trying to kill the Lich King, but afterwards they made her just as expansionist as Garrosh with no mitigating factors. Which just gave Afrasiabi(And other writers, I don’t believe for a second it was just him no matter what Cdev says) the basis to turn her fully into a villain.
The shadowlands stuff trying to pull her away from that just feels like a sloppy reaction to a large portion of the fanbase screaming at them over the BFA stuff. But I think its important to remember that she’s been written poorly for years and years before that.