"Not your keys, not your coins" still applies for decentralised platforms. With Celsius, the contract doesn't maintain this because the contract owner can free

"Not your keys, not your coins" still applies for decentralised platforms. With Celsius, the contract doesn't maintain this because the contract owner can freeze funds at any time. Because of this, your keys are no longer enough to access your funds. You also need "consent" from Celsius to withdrawal. Compare this to a smart contract where the contract owner can't arbitrarily freeze or seize funds, alter state, or upgrade/modify the contract (or at least require some level of community consensus to do so). These platforms can still largely do what Celsius did but with the caveat that everything needs to be done on chain or through some auditable/provable off-chain method. Likewise changes to parameters or code would need to be done using either some consensus method (higher centralisation risk) or manually by users migrating to a new contract (lower risk). Unfortunately the "your keys" part isn't terribly clear in the account model since contracts largely all have global state. The UTxO model on the other hand allows you to more easily analyse state changes and conditions under which you could lose control (if at all) however the tooling on that side is significantly less developed.