This is like saying my car's engine uses oil as lubricant, not as fuel. It's true, but I still have to change the oil every 5,000 miles. So I can still calculate the cost of oil changes into each mile.
Since transacting Bitcoin securely is the utility of the network, just as moving around is the utility of a car, it seems quite fair to judge the energy consumption of the network in terms of energy expended per transaction secured.
It's quite different: the energy represents the market cost of securing the network. The value of the network supports that cost otherwise nobody would be performing mining.
If this were taxpayer supported I could understand the objection, but the people buying the energy to run the system are doing so as a commercial activity to make a profit. How is this commercial use of energy inherently worse than other commercial activities?
Since transacting Bitcoin securely is the utility of the network, just as moving around is the utility of a car, it seems quite fair to judge the energy consumption of the network in terms of energy expended per transaction secured.