That a coin fluctuates in price does not mean it is dead. Price is not a determining factor to the success of a coin in the market, it is the price. Ethereum is one of the most adopted coin, so i do not see any reason for it's death.
Of course, everything happens the way you say. If the entire market falls crypto, the etherium also falls with everyone. If we say that the ethereum is dead, then what about other crypto-currencies? Many projects are built on the ethereum platform and have erc-20 tokens. Then at 90% of the crypto-currencies will be dead, with such reasoning.