Actually that last response I gave to your question was a smart ass response and a serious question does not deserve a smart ass response.
JBJ actually is trying. But look at how good hitters hit and you won't find any of them tilting their heads at the start of their swing the way JBJ tilts his head. Once you've done that you are only going to see the ball so far as it approaches home plate and then you are going to lose the ball. That is why Jackie's head so often looks like he is jerking it around. He is desperately trying to keep his head on the ball because he knows he is supposed to and he knows he is losing sight of it as it approaches the plate. The only hits he gets with this swing will be if he catches the ball way out in front of the plate. Anything else is incidental contact for him at this point. Its luck if he fouls the ball off.
This could be hard to cure for Jackie. He is massively stubborn about his swing. Went through something like 500 AB's hopelessly before he finally relented in 2014 when he was twisting his torso so far toward the 3rd base dugout that you could see his whole back. Remember, they forced him to stomp hard with his front foot, so hard that he could not twist his torso and stomp at the same time? Eventually a normal weight shift and hip turn felt right to him and he got rid of the torso turn. This is a different problem and I just don't know if they can get to him this time. Maybe they can. Honest to God I don't know. He is pretty advanced in age to have this problem.