Wiring and turbines were replaced in 1980's refit so are actually only about 20 yrs old. Subs can launch cruise missiles which have a much lower payload at the cost of $2 million per round. The blast and damage effect of 1 16" shell (which cost around 10K)would require roughly 6-8 missiles to accomplish the mission. The destructive power of the shell is greater than a missile because it arrives with much more force because of its weight, speed, and momentum. Using cruise missiles for shore bombardment is not cost effective and impractical because for the cost of 1 cruise missile we could shoot hundreds of 16 inch shells and destroy a lot more targets.
However, that destructive power does very little good and can cause extensive collateral damage if the shells do not land where you want them to.
The problem encountered with the USS New Jersey in Lebanon in 1983 was accuracy.
The poor accuracy in Lebanon and the 1989 gun turret explosion on the USS Iowa that killed 47 sailors convinced the Navy that the era of the Big Gun was truly over.