The QUAD is an important counterbalance to China’s growing aggression in the region and is perhaps a strategic necessity for India. But QUAD’s capacity to provide an alternative to China in trade is rather limited at the moment.
1)      Supply chains of the 'Quad' nations are a lot more dependent on China than on one another
2)      43 % trading of Australia is with China, which is much higher than second most important partner Japan with only 9 % of total trade.
3)      For Japan, China is one of its leading importers. In 2020 China took in 15.08 trillion yen ($146 billion) worth of Japanese goods 2020, according to preliminary data released by Japan's Ministry of Finance, leapfrogging the U.S. to become Japan's leading destination for exports for the first time in two years.
4)      China is currently the United States’ 3rd largest goods trading partner with $558.1 billion in total (two-way) goods trade during 2019. Goods exports totaled $106.4 billion; goods imports totaled $451.7 billion. The U.S. goods trade deficit with China was $345.2 billion in 2019.
5)      Also, China is the major importer of US Trade service with a trade surplus of an estimated $36 billion with China in 2019.
 
Keeping all those factors in mind, it is a difficult road ahead for the QUAD group to reduce the trade dependency on China. It would be very difficult for these countries to find a cheap and quality manufacturer in near future. Few other countries can be alternative but no country currently has the capacity and resources as China does.  
Another important factor to consider is China is not only the “Factory of the World” but also one of the largest markets in the world.
 
Sources for Data:
·       UNCTAD
·       Australian Department of Foreign Affairs and Trade
·       Office of US Trade Representative
·       Japan's Ministry of Finance