In particular, it's helpful to make a distinction between brute-forcing a cipher, and brute-forcing a particular file. If I GPG-encrypt my plaintext with a weak RSA key, or a weak passphrase with conventional encryption, that particular ciphertext may be revealed through a brute force attack; the attack wasn't on the cipher, it was on my key.
Also, the fact that it's impossible/infeasible to exhaustively search the keyspace doesn't mean that the key won't be found - 50% of the time it'll be found in the first half of the keyspace that's searched (assuming a linear search), 1% of the time it'll be found in the first 1% of the keyspace that's searched, and so forth. Success via brute force isn't at all likely, but it's not impossible, even though an exhaustive search is practically impossible.
In particular, it's helpful to make a distinction between brute-forcing a cipher, and brute-forcing a particular file. If I GPG-encrypt my plaintext with a weak RSA key, or a weak passphrase with conventional encryption, that particular ciphertext may be revealed through a brute force attack; the attack wasn't on the cipher, it was on my key.
Also, the fact that it's impossible/infeasible to exhaustively search the keyspace doesn't mean that the key won't be found - 50% of the time it'll be found in the first half of the keyspace that's searched (assuming a linear search), 1% of the time it'll be found in the first 1% of the keyspace that's searched, and so forth. Success via brute force isn't at all likely, but it's not impossible, even though an exhaustive search is practically impossible.