The waste of electricity/mining gear is mostly due to Proof of Work consensus, but moving to Proof of Stake/other consensus algorithms will eliminate basically all waste (eg. Ethereum is moving to PoS).
From what I can see, cryptocurrency is technologically frozen right now because any change results in some people making less money so there can never be a consensus on anything.
No one has a demonstrated effective PoS implementation yet (that isn't simple centralization). ETH will not move to PoS anytime soon enough to be meaningful, nor will any other cryptocurrency.