Leader of the Forsaken maybe but she’s still my Warchief. Tbf even Sylvanas wasn’t opposed to the Desolate Council she understood she couldn’t do it all.
If anything, Sylvanas’s Shadowlands arc and her already going through the Dark Night of the Soul in SL makes her a great leader and role model in TWW. She’s proven she could be a mentor/friend to Anduin.
Plus her BFA plot with Xal’atath and Azshara would be interesting to revisit.