Energy is useless. Which is not to say that kinetic energy as a concept is not in play but that the calculated quantity is useless in any discussion of terminal ballistics. Until we can determine exactly 'how' that energy is being used, it has no meaning. We do not know how much is absorbed by the fluids and soft tissues of the body, how much is being used to destroy tissue and break bones, how much is being used to deform the bullet, how much is lost through friction/heat, etc., etc.. Without knowing all that, the total quantity of it is a meaningless number and it doesn't take an engineering degree to figure that out.
I'd love to hear an example of where kinetic energy numbers tell us anything useful. Without knowing any other details, is a cartridge/load producing 2000ft-lbs automatically "better" and more effective than 1000ft-lbs? Better for what, deer, varmints, elephant? Can you answer the question without knowing any other details? If you were to push a .357 carbine into elk duty, which would be better, a 125gr JHP at 2100fps or a 180gr WFN at 1600fps? Do you need energy figures to answer that question? Not if you know anything about terminal ballistics. Does it change anything knowing that the 125gr load produces 1200ft-lbs of energy and the 180gr produces 1000ft-lbs of energy? Those are not dissimilar cartridges but two common loads for the same cartridge. Is energy what makes the 125gr a better varmint load? No. It's the lighter construction and higher velocity, ensuring a flatter trajectory and explosive expansion. You can figure all that out without energy. By the same token, if we push that 180gr 400fps faster and thereby increase its calculated energy by 60%, does that make it 60% more effective? Does it make it more effective at all? No. In fact, it could make it less effective by driving the bullet too fast for the material it's made from. Let's make the bullet a monolithic copper solid, does that make it more effective? Perhaps, a little bit but certainly not 60%. So of what use was kinetic energy in figuring all this out?
Let's compare dissimilar cartridges. Is 4700ft-lbs automatically better than 1200ft-lbs when the game is the size of Cape buffalo, hippo or elephant? Is a .375H&H launching a 270gr expanding bullet at 2800fps more capable than the same weight solid out of a .44Mag at a relatively sedate 1450fps? Does having over four times the energy make it capable of taking game four times larger? The answer is a resounding NO. In fact, the .44 will outpenetrate the .375 and break heavy bones without deforming. So tell me again what role energy plays in this scenario? Many have said that 1000ft-lbs is minimum for deer, what about 1200ft-lbs on 2000lb water buffalo?