> After all, the most played competitive shooter is CS and Valve has does not use kernel-level AC.

Valve doesn't employ kernel AC but in practice others have taken that into their own hands - the prevalence of cheating on the official CS servers has driven the adoption of third-party matchmaking providers like FACEIT, which layer their own kernel AC on top of the game. The bulk of casual play happens on the former, but serious competitive play mostly happens on the latter.