The Izd.30 evaluation I read from Maya's CJDBY account. I can't find the exact link atm but I remember the general gist of his evaluation.
All premiere engine manufacturers have a generational lead over China right now. The Europeans are flying the EJ200, US flying the F119, YF120, and F135, and Russia flying the Izd.30. All of them have TWR of 9-10. It's very accurate to say the world has a generational lead over China today. It's a gap I foresee closing when the WS-15 starts flying but that is probably still a couple years away. Countries not on the list are nobodies, incapable of creating their own turbofan and not worthy of mentioning in a comparison with China.
You are right that the generational gap is not strategically fatal, J-20s with 4th-gen engines can face F-22s with 5th-gen engines adequately; it's what their airframe was designed to do from the beginning, but you cannot deny there is an engine generational gap. Fortunately for China, even if the US rushes ahead with 6th-gen engine development, they won't have a good airframe to put it in. An F-35 with a 6th-gen engine will still be an F-35, nothing that a J-20 can't handle.
High-bypass turbofans are of greater long-term importance to China than the WS-15. If the CJ-1000A and CJ-2000 are realised in a timely manner and possess the stated performance, it would be a massive boon to Chinese engine development both military and civilian going into the rest of the century. The Chinese government cannot always be haemorrhaging money by subsidising the engine industry, they need to find their own legs and achieve organic profitability like the shipbuilding industry. You only have to look at the fate of the USSR and current state of US shipbuilding for examples of what happens when industry loses their competitive edge and begins to rely on government handouts. In that regard, the Russians with the PS-90 and PD-14 are considerably ahead and are in a better position to allow their industry to thrive without government funding...... if they had a domestic market that is, which they don't, so they're kinda screwed even though they have engines. But at least they have engines which is more than can be said for AECC right now.
Upgraded WS-10s will never reach F119 performance, they'll barely reach F110-GE-132 performance due to inherent limitations with the design. The high bypass ratio of the WS-10 was a compromise measure to offer sufficient thrust at the cost of high-altitude performance. The turbine inlet temperature of the WS-10 is also higher than usual for 4th-gen turbofans making it more difficult for Liming to achieve a long lifespan which is bad news for a country that was already weak in materials science. The WS-10 architecture really is subpar when compared to its peers, however, it's the only war-ready 4th-gen design China has right now so we'll make do. Despite shortcomings, China is better off today for having chosen a flawed 4th-gen core as the WS-10 basis than a safe and optimised 3rd-gen like the AL-21 or TF30; I shudder to imagine a 2018 China that started 4th-gen development late and is still ten years away from maturing a 4th-gen turbofan. China also had no other choice in the 80s when the CFM56-2 core was chosen, the only alternatives were AL-31 and F100 both of which were inaccessible at the time. If Deng was insistent on ambitious performance specs (he was), it was either use the CFM56 core or create a core from scratch. 1980s China was definitely not capable of creating a 4th-gen engine core from scratch so CFM56 it was. Now that China has the luxury of initiating blank-sheet designs, I doubt the WS-10 situation of inadequate future-proofing will happen again.
