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?
Polkadot can be called a better or upgraded version of ethereum I think. Dev just tried to give a solution to those problems that the Ethereum network can not. But ethereum network is so massive that no project can completely replace it. There are many projects that show great expectation but still, there are not anywhere near the ethereum network.