The response from AA is just fine. What more would you want said and why would it make any difference if someone sat there and came up with however many different iterations there of, "sorry you believe that the service was subpar."

What matters is what AA does with the complaint. If it's forwarded to a crew base manager who speaks with the individual and that person realizes that passengers do complain, that's more than sufficient. If it's the individual's Xth complaint, perhaps AA does something.

Just send in a webform and it will all get addressed in the same manner.