As a security researcher (but not necessarily a crypto one), I do not understand this comment.
> AES in its default block cipher mode can usually be byte-at-a-time decrypted.
1. Block ciphers don't have default modes. Implementations might. Does OpenSSL really use ECB as the default mode? (I agree wholeheartedly with you that sensible defaults are extremely important, and so ECB-as-default seems hard to believe.)
2. What does "byte-at-a-time" decrypted mean? You haven't specified the threat or attacker models.
Are you saying that given several million ciphertexts, you can recover the key from AES-ECB? AES-CTR? Does the attacker need side channel acccess? How about given one ciphertext? Or is this a chosen-plaintext or chosen-ciphertext attack?
In short, could you please detail the attack you have in mind?
> AES in its most "modern" mode ends up being exactly as secure as naive XOR when developers use it without understanding its parameters.
As far as I can tell, this is entirely predicated on your later statement that "nobody does [real cryptanalysis]". What is AES's 'most "modern" mode'? Which parameters are you referring to here (key size, mode, any others?)
My guess is that XOR will fall in some small number of hours against someone who cares; AES-128-ECB (as bad as it is) may require many more resources for key retrieval.
For fun, which definition of security are you using to compare cryptosystems?
