But the entire point is that it wastes energy. That's why it works. It isn't like a car that can be made more efficient and therefore better. The central premise is that we're going to waste energy to do something that can be done in other ways without wasting energy.
The entire point is that it wastes something. Not specifically energy. The idea is that there is a sunk, unrecoverable cost associated with mining. That cost may be able to take other forms, though. In the case of proof-of-stake, that cost is the time-value of money.
