As I understand it (and granted, I haven’t worked with it personally), Hedera just provides a distributed ledger service, which while it’s useful, doesn’t include the smart-contract language/infra provided by Ethereum and its half-dozen similar systems.
(Which is a shame, really. I, for one, would like to see someone build a Turing-complete smart contract platform on top of hashgraph rather than blockchain, if only to have one that’s more performant.)