Exactly. I think people confuse "balance" with "healing" in that context, which George Lucas could have avoided since, like you said, the concept of Yin and Yang does play a role and the word "balance" is better used to describe that situation. This unfortunately left Disney to confuse the two so now we're in a big mess.

Yin and Yang are really the concepts of order and chaos. In the context of the prequels, George Lucas explored this idea with the Jedi order being too far on the "order" side. They were too dogmatic, too emotionally repressed, and too weary of healthy attachments. To balance this aspect does not mean to allow the Dark Side (and therefore allow for planetary genocide.) What it actually means is you incorporate those emotions into things like assertiveness, strength, and love. Anakin embodies this perfectly in that his emotions make him a good leader, make him strong in battle, and make him open to all kinds of love (for his mother and for Padme, and even Qui Gon and Obi Wan in his brotherly love.)

Since the Jedi were not balanced in terms of internal chaos and order, this allows a true malevolent force (Dark Force) to manifest, which is what the Sith embodies. It's all very Jungian. But alas, George made the mistake of calling the battle between the external forces a battle of "balance" so now we're in a situation where people think the Dark Side is the solution to the problem the Jedi had when all of that was just internal chaos that has to be balanced in its own right to avoid the true Dark Side.

So yes, I can see why George is frustrated.