The Forsaken create their state on the basis of mind controlling murlocs, ogres etc. unlike other races who did it by killing those. A Forsaken rando keeps a human mindslave in Vanilla, well before the Cataclysm turn and other random Forsaken praise him for his creativity. Execution or life sentences of people who try to defect to an opposing world power who recently tried to assassinate the leader of your state is, when you strip away the melodrama put into the deaths of those guys (and not, for example, the Forsaken brained by Baine's totem or the guys in the Underhold), practiced by the majority of states in the world.
Sylvanas's consistent breaking of people's mind in Cataclysm consists of raising people with their free will at which point even in the very first zone a sizable portion defect and need to be fought against because they have enough of their minds to rebel and others leave and need to be hunted down to be convinced to join, like Voss. After that, virtually every named character she raises turns on her, be it the Gilneans or Stromgarde. If we extend it to BFA, we can add everyone else to the mix as well. Once again, more people betray Sylvanas for not doing what you allege then turn on her for doing it.
It's impossible to ignore the part about Calia considering she is the thing their entire identity and history are burnt in effigy over and the basis for their future identity unless Blizzard backtrack hard - the Forsaken as temporarily embarrassed living Lordaeronians. The premise of Sylvanas always having used them is firstly something the narrative already tackled better with Cataclysm, where her abandonment of them is followed by being immediately sent to turbo hell. In response, she recommits herself to their interest because it's intertwined with hers and she ends up encouraging Lordaeronian nationalism, picking up dog tags and looking for ways to preserve their race. That her actions were only to their detriment from Day 1 is also only there in the BTS version of the story, where reconciliation with humanity was always an hour and a hug from Anduin away compared to Vanilla where the existential threat to the Forsaken was an object of fact.The end to the Forsaken story in BfA, ignoring the part with Calia, seems to be the Forsaken realizing and coming to terms with the fact that the one they thought always had their existence in mind, and strove ot uphold the ideals they aspired to, was in fact always using them for her own ends.
Why should the Forsaken at this point spin on a dime and accept her back? She has betrayed everything they are supposed to stand for.
Again, we're only here because of a retcon that weakens both the Stormwind and Forsaken identities and sacrifices Sylvanas on the altar of a direction not wanted by pretty much anyone who actually plays the race. To get there, every single Forsaken character prior to BFA had to not exist and the core premise of why they're even called Forsaken in the first place had to be changed to an easily fixed con, robbing the race of their agency. In turn, humans mistrusting undead or fighting to reclaim Lordaeron or even the extracting of justice for the Forsaken's culpability in endless offenses against humans is dismissed so Anduin and Big Titty Light Mommy can make them all friends. Forsaken prior to BTS turned on Sylvanas often and on different bases. Post-BTS Forsaken are dross who don't turn on her even in a situation where she's objectively pure evil and all the benefit she did to them was retroactively void. There's nothing worthwhile in this portrayal and the retcon to nix it would be both more widely approved and much easier to implement than the mess it required to bring about.