Negate isn't a bad word. It describes erasing the threat, which is not realistic in many situations.
Ultaimtely AA is treated like the other ship statistics. Some ships have good armor, others good speed, others good guns, and other good AA. Some ships have AA on them, but as it's not the focal point of the design it's more "functional" than "exceptional". This can be frustrating because when you have a game where there is no CV, the lack of AA strength has no bearing on ship performance... but it absolutely matters when a CV is present.
The Musashi is an extreme example of a Very powerful Tier 9 when no CV is present, and a babysitter-required liability when a CV is present.