But this is almost the appeal to consequences fallacy. You’re saying no free will means no ethics. Well, perhaps “right” and “wrong” must start to mean something slightly different from our prior conception when we realize that free will is nonsense, but that does not save free will. We must simply rethink matters. In fact, I see no reason that the absence of free will negates ethics. If I kill someone, although ultimately I could not have done otherwise, it was still wrong to do it. A criminal justice system can still be either just or unjust, even if ultimately that criminal justice system itself (the product of our communal decision-making) could not have been otherwise.
But, ultimately, I think you’re saying - if there’s no free will, why bother?
I think the best analogy is this: our visual system incorporates many illusions generated by our brain that allow us to interpret the world - we do not “really” see the continuous perfect picture that our brains tricks us into thinking we’re seeing. But, although it’s interesting to learn about this, it would be crazy to start trying to subsequently try to use our eyes differently for practical purposes. Obviously our visual system evolved that way because it works well.
Similarly, our brains developed the illusion of free will in decision-making. All that we are really doing is processing data and generating output, but perhaps the illusion of deliberation and agency leads to better decisions. Thus, as in the point you made earlier, even though free will is an incoherent idea and does not exist, it would be silly to try to actually fight the illusion of free will as we make decisions every day. I agree that the world seems strange and uncomfortable in certain ways without free will, but ultimately we just shrug our shoulders and get on with making decisions as best we can, including arguing for an ethical justice system.