The only reason that proof of work proves anything is exactly nobody likes throwing away electricity.
The degree to which PoW is undesirable is precisely the degree to which is is useful.
See also:
https://en.wikipedia.org/wiki/Handicap_principle
Satoshi's PoW plus coinbase mechanism was a brilliant method to start currency distribution and ensure decentralization with no central point of failure. I have spent four years brainstorming if another mechanism could have done the same and have come up with nothing, the insight he brought here was just brilliant.
That said PoW mining on a large scale is wasteful, and sometime after the currency is mostly mined (i.e. fees have taken over rewards) and has had time to distribute throughout the economy, alternatives may be valid to look at.
The entire point of PoW is to fairly distribute votes among individuals in manner that is entirely within the system with no external dependences. For example if everyone mined on their personal computer (and only their personal computer), then what PoW does is it randomly selects an individual to create the next block.
This distributed block construction ensures decentralization.
There are other mechanisms to achieve the same effect after coins are mostly mined, and if alternatives can do so without wasting a ton of energy they should be considered at some point (not today).
For example bitcoin could switch to a voting mechanism based on btc held. This only makes sense after wide distribution, but it would achieve the same decentralized block creation mechanism where individuals are randomly selected to create the next block, and bitcoin exits entirely within itself.
It might actually help decentralization since individuals would have less reasons to use a pool. Today since mining electricity costs are close to revenues, miners have to use pools to stabilize revenue. If there are no costs (other than saving you money) then it is easier to solo mine and risk it.
These are questions for another day, but I think it is important to see PoW as a fairer bootstrap mechanism with other mechanisms that could achieve the same ends