There are several delegated Proof of Stake cryptocurrencies which achieve similar results as PoS and have been running successfully for years. E.g. Lisk and EOS

There are several delegated Proof of Stake cryptocurrencies which achieve similar results as PoS and have been running successfully for years. E.g. Lisk and EOS. The reason why Ethereum is taking so long to move to PoS is not because PoS is impossible but rather because a seamless migration between PoW to PoS is challenging. If they implemented PoS from scratch, it would be a lot easier.