Naples offers so much to see & do it is nearly impossible to fit it all in. And if you have many ships in port the lines & traffic will slow you down.
I have been to the area 4 times now & finally have done all the sites you mention.
Finally got over to Capri this cruise. Lovely island. The Amalfi Coast Drive is something you need to see too. Stopping along the way to see Sorrento & Positano.
Hard to imagine doing a little of Pompeii, but, guess if you set a time limit you may be able to stick to it. Again the crowds may influence that too.
Good Luck & ENJOY your cruise.
PS Check out my 2 new webshots albums to see my photos.