Modern ships and submarines, fighters, tanks etc take longer to build than there WW2 counterparts. While smaller ships can tend to be ramped up, large major combatants were painfully slow even with a full war economy going. Fletcher class was a 2,000 t ww2 destroyer with a whole bunch of 5"s. Battleships for example still too 4-6 years to build and even with the pressure of full on high intensity war, that wasn't really increased. The ones that were rushed tended to have significant flaws either in design or construction. There is a reason why US still builds so many supercarriers, you can't just rush ships like that into production.
Australia's strength isn't in manufacturing capacity, which is really a function of economic power and size. We tend to build solid units that meet our unique requirements. But in comparison to the major powers. US or Chinese ship production is other dimensional. We don't compete in that space, no one does.
IMO with the 3 production lines, Australia is in a good position. Its more about sovereignty, independent policy, sustainment and local economic benefit. In a world where the major powers are frustrating to deal with, having our own production line, ships coming and out of service is important. When we talk to Indonesia, Philippines, Vietnam, Malaysia, New Zealand, Singapore, we have capability. It doesn't matter what everyone else is doing. We aren't completely dependent on US congress line items and priorities, we aren't dependent on UK policy working in our favor for every day operation. We are independent enough to do our own thing if we need to, and lead it.
