Why do you think China struggles so much with turbine/dynamic systems technology.
Conventional wisdom is that engine design remains something of a craft, due to the fundamental physics involved, and is difficult to break into without learning the hard way what works and what doesn't. While there are dozens of companies worldwide undertaking component design/supply and local assembly these days, few have made a success of breaking into the whole engine business, Williams perhaps being the last company to make it (with the benefit of experience gained through the production of several thousand cruise missile engines).
That's not to say that China won't get there, but it's not as straightforward as copying an airframe or an avionics board.