Which is actually what she was doing with all those forces. They were there to assist the PC in securing the Aegis to use against the Legion. She went after the lantern as a solo mission.
Also, Genn didn’t do a good thing, from a Horde perspective. Sylvanas was trying to solve an existential problem for the Forsaken - how do they survive if they can’t reproduce and they will eventually rot? Per her own internal dialogue “I would have saved them” had not Genn intervened.
What he was doing was a good thing from his perspective and an Alliance perspective. But also genocidal and evil from a Forsaken perspective (certainly from Sylvanas’ PoV).
Which is why I thought that particular sequence of events was faction conflict done right. That really was an example of “morally grey” on both sides.