Excellent sum up of not your keys, not your crypto. Totally in agreement.
That's why we need DEX (Decentralized Exchanges) & New technology continuing evolving and solving these problems. If can have a DEX that allows it. DEX do need liquidity pool for quick transaction. Can there be other ways a dex can act like a smart contract in a decentralized way such that no one is able to give permission to others to handle crypto? It is a good question to start.
Regards.