I am saying that you go with the worst case scenario until you have actual data to work with.
Personally, I think hitting a maneuvering ship with the payload from a ballistic missile going to be tough - but we have managed even more impressive things and losing 6000 sailors to find out that their ASBM works and our ABM doesn’t is going to be an awfully high price.
And I remember reading how the USN didn’t respect the equipment and expertise of the IJN. I don’t want to see a repeat of that either.
I'm no expert on ABMs, but I do remember when Pres. Reagan started "Star Wars" ABMs in the 1980s.
Seems like there are three different categories -- 1) Booster phase 2) outer space and 3) reentry phase, and the idea is we have weapons to defend at each phase.
Aegis & Patriots are for reentry, other weapons try to stop them sooner.
My point is the US has now had about 40 years to think, design & build anti-missiles and so far nobody claims we have an "iron dome" to stop all incoming.
But they do say we can stop some, and my guess is we'd stop more than they claim -- still not a perfect shield, but enough to make our enemies pause & think twice.
A failed attack on us would be worse than no attack.