Dong Feng 21. Ships currently have no defense against a ballistic missile attack.You've clearly not bothered to actually educate yourself on things or even to bother to read any replies in the topic that you didn't already agree with.
Targeting a ICBM or a missile in that class on something that moves is a non-trivial problem, guiding it through the fireball of re-entry at mach 15 to such a target is again a non-trivial problem and there is good reason to doubt it has been done or how well it works. Anything less than an ICBM is a considerably easier target and while it's not an easy task to stop one, it has been done and anti-theater level missiles is one of the main tasks for Aegis equipped ships. You might be too young to remember the gulf war, but it's been more than a quarter century since that and the technology has only gotten a LOT better since then.
There's a good reason why in the past they've been designed to attack immobile objects and generally large densely packed areas like cities. It's a vastly simpler task and much easier to do precisely.
You also have a poor grasp of scale. The ocean is big and a fireball a few miles in diameter doesn't cover nearly as much territory as you seem to think it does. Ships in a battle group are typically several miles apart. Those nice tight little formations you see in pictures are just PR photo ops. They don't cluster up like that in operation, for precisely the reason that you don't want them all to get taken out in one blast.