That's the point. Cardano has been extremely slow in development, which has left the project behind others that are highly active and supported by their communities. Ethereum still has the lead, because it always delivers (although the promised Casper PoS still hasn't been activated yet). This way, Cardano will never destroy Ethereum, staying behind the leading cryptocurrencies for a long time.
Still, there's hope for Cardano if releases its VM for smart contract functionality. Only then, Cardano can be compared with Ethereum as it will have the same features as its rival. With many smart contract platforms available today (such as NEO, EOS, Waves, Tezos, Tron, and now Stratis), it'll become extremely difficult for Cardano to stay ahead in the competition.
Therefore, I believe that Cardano will not destroy Ethereum but rather complement it over time. Just my thoughts