You need opportunity cost in order to secure the network. Without that, there is no incentive to keep the network secure. There is no cheaper solution to solve this problem, therefore there is no waste.
You also need to remember that bitcoin is upgradable. If in the future we find better ways of doing distributed trust, and we can prove it, that doesn't mean that bitcoin is done and gone. If the vast majority of the users of bitcoin believe a change to whatever other "distributed trust" system that is better, the network can be upgraded to take advantage of it.
I mean in absolute numbers, says the bitcoin advocate, the fiat banking system has to use more, right?....
....nevermind the fact they do something that is not driven by pure speculation and do it at thousands of times larger scales.
Bitcoin -- the perfect intersection of people who don't understand finance, economics, computer science, scaling, politics, socio-economics, or math.
PS: People only quote Bitcoin's energy use and often times they leave out things like air conditioning. Nobody seems to sum up the total energy required to power the entirety of the crypto "space" including Ethereum, Litecoin, etc.
What you may call waste is in a way the cost of the operation of the network (and its properties and guarantees and so on).
Waste suggests that there is an easy, equivalent, much more efficient solution around the corner but no one cares and wastes resources instead when they could have been doing the same thing with fewer resources.
I mean, I understand (I think) that Bitcoin doesn't require a given node to trust another node. But what if there is a change to the software that trickles down to all the nodes without them realizing the consequences until it is too late? Either a bug or intentional subversion.