So the backup isn't unencrypted like you claimed, that could've easily deduced if you mentioned the backup's file name.
Note: The "aes" between wallet and the extension indicates that its payload is encrypted.

Do you have a backup of your account recovery phrase? (various number of words)
That can recover your password and wallet ID, here: https://login.blockchain.com/wallet/forgot-password (do not paste new 12-word BIP39 seed phrase)

If you don't have, you must remember a large portion of the password that you've used so bruteforce would be possible.
In that case, try BTCRecover: https://github.com/3rdIteration/btcrecover
Refer to the link in the reply above for the documentation.