The main problem with the ETC is the lack of backward compatibility with the Ethereum Hard Fork. All the heavyweights of the Ethereum community have moved on to the new chain, which means that anyone who is part of the ETC won’t be able to access any of the updates done by the ETH. The perfect example is ETH’s move from Proof Of Work (PoW) To Proof of Stake (PoS). ETC won’t be able to implement that because their software simply doesn’t allow the use of updates.