Try to get your wallet.aes.json by pasting your walletID to this URL:
Replace "WALLET_ID" with your Wallet ID, do not change anything like the punctuation marks.
If you didn't set 2FA, the URL will display your wallet.aes.json in txt format (if you have 2fa, use the method below).

With it, create a "wallet.aes.json" file and paste the text using a txt editor, then decrypt it using decryption tools.
This one should work: https://github.com/blockchain/my-wallet-backup-decryption-tool/releases
But the private key from the result isn't WIF (Wallet Import Format), it's in base58 form.

If you successfully decrypted the wallet file, you can convert the base58 private keys into WIF by using base58 decoder and then convert the result ECDSA PrvKey into WIF (compressed) to be able to import/sweep it to other wallets.

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Another method to get your wallet.aes.json file is to use btcrecover's extract-script: download-blockchain-wallet.py from https://github.com/gurnec/btcrecover/tree/master/extract-scripts