Why do I feel input lag in Valorant despite having high FPS?

It was a strange feeling; my FPS was over 300, but the feedback from clicking the mouse felt muffled, as if there were a film over it—a fatal input lag in competitive play. I first tried closing all background software, but the response speed only improved by 1ms, which did nothing for this low-level scheduling issue, leaving me very discouraged. I used the GamePP Resource Scheduler to set the memory allocation strategy to Low Latency Priority and disabled the CPU C-State. RTSS showed frame generation time converged to 2.8-3.5ms, and memory temp was 52-58℃ per AIDA64.