It's actually the reverse: designing is easy, but actual production is difficult. Certain neighbor south of China is a good anti-example. That neighbor has a lot of designs, but can hardly bring any of them into production.
To build a vessel, you weld modules together. However, the devil is in the details. Here are some issues for you to nibble on:
- How to ensure hundred of modules can be fitted together and aligned perfectly?
- High-strength steels have special welding requirements. How would you maintain welding conditions so that the steels don't lose their high-strength property? How would you ensure the quality of your welds?
- When there are different types of metal used, they accelerate corrosion. How would you prevent that from happening while still being able to use different materials?
I fully concur with this one.
I remember vividly about a Discovery Channel documentary I've once watched. It's about the construction of Bush, the last Nimitz Class carrier. I was deeply moved by how each and every worker interviewed took so much pride in their job and do their job well, for tens of years. Some of these men are generations of ship-builders, whose parents or even grandparents all worked at the very same shipyard. I saw this kind of tradition, pride, and professionalism in documentaries about Rolls Royce engines and Lamborghini as well. To me, I feel that an army of highly skillful, highly responsible, and highly professional workers and technicians who truly enjoy and take pride in what they do, is the most valuable assets to any industrialised nation.
Workers and technicians aside, to build world-class carriers on schedule, you need world-class shipyard management and world-class ship-building techniques. We have seen that Chinese shipyards are capable of delivering modern frigates and destroyers in batches, each within almost the same amount of time; it will be another great challenge for the shipyards to delivery the same kind of results for carrier building.
To me, what's truly amazing and admirable about US carrier-building, is not exactly that they can build state-of-the-art war machines like the Enterprise, Nimitz, or Ford. What's more important is that they can serial produce these carriers, and complete each one within a reasonable period of time which is highly predictable (the same can be said about Japanese shipbuilding actually, it's just that they haven't demonstrated this capability in building carriers, though I really don't doubt they can do it).
For China to really grow into a formidable naval force in the world, we need to have this kind of ship-building capabilities. In short, the capability to produce highly sophisticated carriers with little to none major hiccups or problems, in batches, over a span of decades.