I know I'm a bit late to the party, but this is where the issue lies :
While IW4x is a client for a game that natively supports ReShade (COD:MW2), the client itself doesn't. Reason being that the anticheat built with it throws a fatal error whenever anything hooks on DirectX libraries, except for a few hardcoded exceptions to allow (some) recording softwares. It's still possible to launch the game through Steam and the game would actually launch instead of crashing, but none of the shaders would compile, thus resulting in the D3DCompiler error that this topic is about.
However, I've heard that some older versions of ReShade would work. But for testing with the lastest 2.x, 3.x and 4.x versions with no success, I can't be really sure about these rumors...
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