Sylvanas and her old regime is over. The Forsaken that survive today are a minority of the original population who have been beset with failure for much of their time as free willed undead. From Varimathras to the Fourth War. The Forsaken were already depleted during Cataclysm hence why Sylvanas began raising new undead and especially former Alliance partisans. The people of Silverpine and Hillsbrad. Not to mention the Darkfallen of Darkshore etc.
Right now, the Forsaken of today are very different than the ones who first founded the faction under Sylvanas. If the new Forsaken under the Desolate Council want to go in a different direction that’s something we all have to accept. More so, the Forsaken population isn’t numerous enough to dictate the terms to the Alliance or to act in a way that violates the Fourth War agreements. They were allowed to rebuild in Tirisfal post Fourth War and as we can see in-game the population is far smaller thanks to Sylvanas. Her loyalists are done. They’ve been arrested and those that remain are generally not in positions of power to dictate anything. I doubt the Night Elven Darkfallen and the resurrected victims of the Fourth War and since the Cataclysm will be so eager to commit themselves to the old regime’s ideals.
As Garrosh said, “Times change!”