Originally Posted by
Triceron
That can be a criticism of the story overall, but not of her actions as a military leader. Nothing about that poor BFA writing contributed to her being a poor Warchief (Dictator).
"Something" marks it as bad, so what exactly would you specifically frame as bad about her leadership in battle? The story was just as easily throwing in random elements like Jaina appearing with a floating battleship, so I don't know what you would consider competent military decision making in this context.
I agree that Sylvanas was not portrayed as a brilliant military leader, but neither was she written poorly for it.
Vol'jin, in comparison, was straight up written poorly. He leads the Horde in Broken Shore, and gets killed easily and randomly. Sylvanas in comparison would be a poor Warchief if she allowed Lordaeron to be taken or let herself be captured, but she did not. She lost Lordaeron but did not allow Alliance to take it, and that is the best thing a commander could allow in war. The only real loss she got was from not dealing with Saurfang, which lead to her failed plans with Derek Proudmoore and ultimately losing her position when she finally fought Saurfang.
If welfare of troops is the standard of a good commander, then Arthas would have been the worst commander ever since all his troops are dead.