I've looked around extensively for a solution to my problem but unfortunately in every case I've found the "solution" is that the game simply uses 1 processor core fully and only barely touches the other cores and everyone goes "Oh yeah I see that my first core is all used up that explains it"

Unfortunately for me this isn't the case. I get 20-30 fps in cities with around 50% of my first core being utilized and less than 15% of the rest, and only 20-50% of my GPU being used depending on whether I'm playing in 4k or not. The framerate doesn't change at all between 1080-4k so I know it's a processor issue but with such small utilization of it I'm wondering if there's any way to make it use much more of the only core it seems to be using in the first place. I would much rather it use 90% or more of that core and have at least over 30fps in cities.

I could understand if it were doing that so as to not overheat but the processor doesn't even go above 55c so it's not a heat issue, either.