The reason for the inability to crew these ships is much more complex than saying because the RN has two large aircraft carriers.
The RN has a huge problem retaining people. That has nothing to do with carriers and everything to do with Conditions of Service. I work with the RN every day, my son is a serving RN engineer so I think I may be reasonably qualified to comment.
In the job I do, I have seen multiple CPO engineers up and leave at the 15-19 year point. Some of which have been highly motivated individuals who the RN should be actively trying to retain, but the apathy that comes from the lower end of the leadership scale (round and about SO2 level) is breathtaking.
Another factor is the change in pensions. Staying till the 22 year point is no longer worth it, as there is no benefit; especially with a vibrant job market on the outside. When these changes were made, it sent a signal to many (me included) and leaving was absolutely the right thing to do.
Any Service is only as good as its people, leaders should be aware of this.
But don’t blame the Aircraft Carriers, the rot set in long before they were on the scene.