Energy in physics feels analogous to money in economics. Is a manmade medium of exchange used for convenience. It is the exchange medium between measureable physical states/things.
Is energy is real in the same way money is? An incredibly useful accounting trick that is used so frequently it feels fundamental, but really it’s just a mathmatical convenience?
Small aside: From this perspective ‘conservatipn of energy’ is a redundant statement. Of course energy must be conserved or else the equations are wrong. The definition of energy is it’s conservation.
Yes it’s manmade concept because people are made from matter so they use energy as a matter representation ignoring everything else that doesn’t have matter. Looking at you SI. 1 Joule = 1 J = 1 kg⋅m2⋅s−2 is amount of work done when a force of one newton displaces a body through a distance of one metre in the direction of that force. So you can see you need a weight, a distance and a time. Given that in quantum world distance is infinite, time and weight is 0 it’s completly manmade product.