The Chinese haven't been able to clone the Russian engines yet. Metallurgy at those levels is very tough. And Russian engines don't match what's currently used

The Chinese haven't been able to clone the Russian engines yet. Metallurgy at those levels is very tough. And Russian engines don't match what's currently used in US fighter aircraft. Passenger jet engines don't really map to fighter engines. It's like comparing an F1 race car with a Volvo semi.