Most things in industry you cannot learn without actually putting products into mass production and then fixing and changing the process.
Design is great but if you design something you can't make in an industrialized way then what do you have? You have an experiment not a product
The WS-10 is a product. So is the J-10. They both got progressively better through the mass production process. What is learned with the WS-10/J-10 is put into other products so that new engines and airframes are developed faster and faster.
Counting civilian engines, China has over around 13 turbofan projects happening right now in every segment of the market from light trainer engine to medium and heavy fighter ones to high-bypass poweplants transports and airliners -- most of them already on testbeds.
China cannot do this on a fake economy or fake technology base like a lot of Indians here try to convince themselves. They cost billions and need a huge technological and industrial base. India could only fund and attempt to develop one medium engine during that same period.
BTW, China is still a developing nation. Manufacturing hadn't peaked in China. Wait for aircraft engines, spacecraft, airliners and cruiseliners