The basics are pretty distributed, further work involved increasing lifespan at high temperatures, but also some work towards switching at least some turbine stages from separated blades into "blisks" - entire turbine stage is one crystal, including the hub.

As hard as ever. US and USSR and EU has this tech, China, India and others still don't. When USSR tech was sold left and right in 1990s, China could not replicate it, although they surely got the documentation back then. Even now they can't build a reliable gas generator from 70s and are stuck at 1960s level with R-25 MiG-21-style engine replicas. They still try and fail to build AL-31 analogs (1978, Su-27 engine).