Exchanges are not at all secure. We must avoid keeping money in exchanges, whether it is centralised or decentralized. These resemble a market where you can only transact. You run a very high danger of having your money or cryptocurrency stolen. So, absolutely, use them only as necessary. Additionally, as is always recommended, keep your money in offline or hardware wallets. If you don't, nobody will be able to stop you from losing your hard-earned money.