It's incredible that people on HN, a technical readership, still don't understand why the energetic or computational "waste" of proof-of-work is needed.
There is simply no other known way of implementing a decentralized, censorship-resistant, robust digital currency. Without PoW you lose one of these properties.
Proof-of-stake doesn't work. It isn't robust. Eg. PoS cryptocurrencies can't resolved which chain is correct after a network split. There are many other unsolved problems. That's why Ethereum is years behind schedule in designing and deploying PoS.
Replacing PoW with a useful algorithm (eg. protein folding) loses decentralization (a central trusted authority must verify/sample who performs the work correctly).
Trust-based systems (Stellar, Libra) lose censorship-resistance.
A "dumb" PoW is literally the only practical solution.
If the social benefits of a cryptocurrency are worth the computational power, and if PoW is the only technical solution to implement it, then by definition PoW isn't wasteful.