RDR2 locked at 20 FPS, GPU not being utilized (Ryzen 7 / RTX 4070 Super). Any fix?

Guys, I have a crazy issue with RDR2 on PC. I'm running a Ryzen 7 7800X3D with an RTX 4070 Super and 32GB of RAM, but the game is locked at a terrible 20 FPS as if the GPU isn't being utilized at all (stays at ultra-low usage). I've tried both Vulkan and DX12, but nothing changes. Can anyone help me out?