The West is giving mostly ancient weapons to Ukraine you say? Do you consider Javelin, NLAW, Stinger, HIMARS, Leopard II, Challenger II, M777, M109, etc as ancient? They don't look that ancient to me.
Well the Europeans seem to consider the Russia-Ukraine war as an existential crisis for Europe, akin to WW3 itself. The Europeans in general, don't seem to mind America blowing up the Nord Stream. They don't mind their industries closing down, moving to the US and elsewhere. Many have even volunteered to fight and die in Ukraine. As far as I can tell from the Europeans, they are doubling down on defeating Russia in Ukraine. It's looks to be quite personal for a lot of them.
The West, as far as I'm concerned, cannot mobilize into a proper war economy like in WWII. Their general populace could not accept any further hardship. Especially if they're government-mandated. Just look at how they behaved with Covid. Even today, there are Europeans on the streets, protesting their economic hardships. Europe today, is miles away from implenting a war economy. Imagine a war with China, where the world's supply chain as we know it is essentially FUBARed. There will be scarcity in all sorts of stuff that the average Westerner takes for granted. Can the average Americans and Western Europeans today go back to WW2-era rationing?
The F-35 production run is much further down the road than the J-20. Plus, there is that big international order book for Lockheed Martin to fulfil. The J-20 production run is not there yet, but China has massive capacity for ramping it up. China can buy the J-20 cheaper than the US can buy F-35s. Because Chengdu Aerospace Corporation is state-owned, while Lockheed Martin is a private corporation that co-owns the US government.
The US appears to be pretty much in a war economy already. What little heavy industrial capacity in the US is now focused heavily into its MIC. The US does not produce railcars like before, but can produce new military vehicles. The US shipyards don't build large commercial vessels anymore. But it can build aircraft carriers. There is not much more potential for the US to ramp up military production. Not like the potential that China has.
The US struggled to ramp up production for even 155mm artillery ammunition. The Pentagon wants to ramp up production, but it needs to give more money to the MIC. Because the defence corporations won't invest their own money into building up their own capacity. Why not just lobby the US government for that money instead. In addition, the defence corporations have, and will massively markup their products, because they love big fat profits. The US defence spending will go through the roof. This is not the FDR era. The American economy is extremely unhealthy. Its capacity for massive deficit spending is not the same as in WW2.
China can easily outproduce the US when it transitions into a war economy. The way China mobilized so rapidly during the early days of Covid gives us a hint as to how readily it could transition in times of war.
China's war doctrine is not about power projection into the far seas, but to the near seas. They don't need to outproduce the US in SSNs, bombers, and CVNs. They can focus on the cheaper stuff, like missiles, drones, fighters, SSKs, etc.
Yes the US forces near China can attack the Chinese shipyards. That is why China extended its A2AD coverage relatively far away from its coasts. Extending into the SCS, ECS, and Taiwan. The US and its allies will have to go through the island bases, PLAN, PLAAF, PLARF, and PLA shore defences just to get to the Chinese shipyards. That's gonna cost a lot of missiles, drones, aircrafts, ships, and skilled personnel. And even if the Chinese shipyards are struck, its not gonna take too long for China in wartime mode to rebuild and repair them. China's production sites for munitions, SSK, fighter and land systems are located much deeper inland. Those are even harder to reach. China is a vast, continental country that also happens to have a modern military. The US is gonna exhaust it's long-ranged precision munitions in the Pacific theater much quicker than it thinks.
It doesn't matter that the US can strike China's shipyards, while China cannot do the same to US shipyards. China's warplan is primarily defensive. Its main objective is to defeat the enemy's threat of power projection near its territory and to keep China safe. Preferably at greater cost to the enemy. That is the priority. China can think about striking US shipyards later, when it is able do so.