In a major shooting war against Russia or China yeah they are vulnerable, they always have been. However, in the type of wars the US has fought since WWII they have been invaluable from air support to a huge base of operations. HST needs to be refueled and continued to be used as before. The price to refuel is worth it in comparison to the strain it places on the remaining fleet.
All that being said the USN needs to find a way to extend the range of their aircraft. The F-18 and the F-35 simply do not have the range the old F-14 and Intruders had. Further the USN needs to invest in improved missile defense technology for the carriers and escorts. I understand they have installed on most of the existing carriers a torpedo defense system that has been excellent in test.
If they decide after the purchase of Enterprise they need to change the direction of naval aviation then do so, do you need a smaller carrier and less planes, do you need a smaller nuclear carrier or fuel oil fired? Can the American class operating F35’s handle the needs the Nimitz and Ford class does?
a torpedo defense system that has been excellent in test.
But later failed miserably and was torn out.