It's true that western engines are more durable, I never denied it. Is this a proof that Russian alloys are decades behind? No.
Is it a proof that Russians have durability issues? Maybe, or maybe its a cost issue not to go for more durable ones.
Maybe Russians sacrifice durability for a lighter engine with higher thrust levels.
Maybe Russians operate the design at levels closer to the maximum, lower life-time but have more thrust available.
Maybe TBO would be closer to western levels if they restrict the engines to 80% power during peacetime while still being on-pair to western engines
Maybe Russian doctrine has lower training hours for pilots due to automation/IADS and simulators.
These are all factors which tell us that Russians are not decades behind, just go their own ways.