Some of my top choices have already been mentioned but one class that not only should gave been constructed, but STILL needs to be resurrected in a hurry is the CG(N)-X.
25,000 tons, 512 VLS tubes, BMD capable, nuclear powered so it can operate current and forcast 2nd and 3rd Generation Rail Guns and Directed Energy systems.. Plan was for 19, I'd argue for at least 26, two per CV(N)BG and three for independent SBG use as floating THAAD with two-three DDG-51 Block III/IV. The world is still a very unfriendly place and the U.S. is riding too hard on 1990s tech into the third decade of the 21st Century.
Another gaping hole in the USN inventory is shore bombardment. The fleet needs to come up with at least a 155mm armed design, although a 208mm would be better that can provide useful naval gunfire support, not just with the gee-wizz 100 mile deep strike but with conventional rounds as well. Ideally a variant of the CG(N)-X but with a much smaller VLS, say 96 compartments, four 155mm/208mm guns and space/weight saved for both rail guns and directed energy. Need at least one of these, ideally two+ for each 'Phib group.