Polkadot offers better scalability than the ethereum blockchain. It offers relay chain, cross-blockchain features, forkless network, decentralized governance and all these are not available in the ethereum network. Actually, Polkadot offers all the solutions to those problems that the ethereum network can not. So many projects are using the Polkadot network. Do you think Polkadot is really Ethreum killer?
Well in the crypto industry everything is possible. By the way, Polkadot is just one of the many competitors that want to dethrone the King of smart-contract which is Ethereum, But as we all know in the crypto industry old platforms has a lot of supporters thats why it's also an important factor why Ethereum is the leading smart-contract service provider.