I have the same problem, here a fix that works for me.
Enable Frame Gen (for nvidia cards).
I have an 13600k and a 5070ti.
The 13600k sits at 50% usage and my GPU is still not getting used.
If your cpu is at 95%+ usage, then it could be a CPU bottleneck that you are experiencing.
My frame without frame gen are 100-120fps on high setting, while gpu is used 50-60% and cpu 50%.
With frame gen (x2), my gpu is used 98% and my fps are 260-280. CPU is still sitting at 50%.
Frame gen x2 just renders one AI Frame for every normal frame, so in theory, my FPS should only roughly be doubled. For me, its more than that. So my frames without frame gen should be 140+.
I guess its a bug, that for some users the gpu is not ultilized right without FG.
FYI: FG doesnt seem to increase input lag much. Im really sensitive to things like and i did not notice any more input lag than when im not using FG ingame.