It is good to use an open-source wallet for better safety options. However, a wallet has been an open-source wallet is not enough to guarantee the wallet as the best or good crypto wallet.
Open source simply means that the code is open and anyone can verify it, using an open source wallet is not foolproof, but it is obviously better than using a closed source wallet that nobody has verified. An open source wallet that is well reviewed and self custodial is surely better than a closed source wallet, however your funds is only as safe as the device it is stored in, so for better security the wallet should be used in an airgapped device and the user must have goof opsec.