I think the reason people rate Cardano very high is because of Charles Hoskinson who was one of the main developer behind Ethereum in the early days. If by now Cardano has not released major project on its platform, then I don't think people would want to migrate to their platform again especially in a crowded market like this
It's also why it's being called its killer. This is a supposed to be aggressive advertising.
Charles had a disagreement with Vitalik and they don't like each other too much. He made Cardano to be a competition but was a bit too late because Ether had already exploded.
Soon after, disagreements arose about how to structure the project. "It was a boardroom brawl," he says. Hoskinson wanted to accept venture capital and create a for-profit entity with a more formal governing structure. Buterin wanted to keep Ethereum a nonprofit organization with an open-source, decentralized governance. Hoskinson left Ethereum in June 2014.
"At the time I was pretty pissed off," says Hoskinson, 30. "Ether went up [to a market cap of] $120 billion, so what the hell do I know?"