RPCS3 (almost) not using GPU

GPU usage reader is wrong, I've seen Task Manager report 0% usages as well in the past whereas that would mean you'd not be drawing anything to screen at all, try GPU-Z instead. RPCS3 doesn't have software-based renders.

For easing the CPU bottleneck, try decreasing SPU thread usage by changing Max SPURS Threads on Advanced Tab to 5, then 4. You need to try values decrementally and check if the game still works. If you change it to 5 and it doesn't work, then you can't change it at all, it depends on the game. If you change it but there's no difference, then the game doesn't use SPURS threads.

Alternatively, show a screenshot of RPCS3 with Performance Overlay enabled in Settings with the highest level of detail.