Here is an article that some may agree.
It's not about the quality but the ability to make them in quantity.China is behind on production of its most advanced fighter jet
China will need to speed up the production of its most advanced Chengdu J-20 stealth fighter jets, with the supply of the "Powerful Dragons" well behind demand, military analysts said.
On Sunday, the People's Liberation Army Air Force posted a video on its social media accounts that featured two J-20s in a combat training scenario with two J-16s and a J-10C. The jets belonged to the Wang Hai Air Group, named after an ace Chinese combat pilot who served in the Korean war.
This type of five-plane formation was seen for the first time in the video to mark Lunar New Year. State television reported that the air force tested a combination of one J-20, one J-16 and one J-10C in 2018.
The latest video showed the "kaleidoscope of tactics" the J-20 and the other jets are capable of, according to the Global Times.
The fifth-generation stealth fighter jets served as the "backbone" of the nation's air combat capability, the air force said on its 70th anniversary in November.
China would need between 100 and 200 J-20s at least to maximise mission flexibility, according to Hong Kong military commentator Song Zhongping.
"The J-20 can tackle enemy radar with its stealth capability or attack enemy planes for air [weaponry] superiority from beyond visual range," Song said.
China was thought to have built about 50 J-20s by the end of 2019, but problems with the jets' engines delayed production plans. Chinese engineers have been developing high-thrust turbofan WS-15 engines for the J-20, but that work has fallen behind schedule.
In the meantime, the J-20 is understood to have used either Chinese WS-10B or Russian-built AL-31FM2/3 engines, compromising its manoeuvrability and stealth capabilities at supersonic speeds........ to read more,