The effectiveness of WW2 ammo might not be so good, but there are improvements that can be done, like cluster munitions.
For beachhead fire support, I'd also like to see something like the Army's Multiple Launch Rocket System. The ATACMS variant has a range of 165 to 300 km (depending on payload size). I'd think that a ship that could cycle a block of missiles out of a cargo hold, launch, and grab another block could put an impressive amount of ordinance on target.
There's a bunch of potential trouble spots where all-weather ship-to-shore firepower might be very handy, North Korea, China and Taiwan being the ones which come to mind first
Far be it for me, who was never really in the military, to question the above, but I was always under the impression that naval gunfire, notably from even destroyers, did some real good on D-Day (in Normandy) of immobilizing some of the Germans by making them keep their heads down. I also read in Band of Brothers, and Dick Winters' autobio, that his doctrine was for some of his men to lay down the thickest field of fire possible while the others went in to take the objective.
So perhaps the effectiveness of bombardment is limited in terms of casualties produced, but the keep their heads down factor is an important one IMO.