@DesertedGnu4296
Hi, & welcome to the forums. 
w.r.t. posting a new question, you probably could not create a new topic because you are new to the forums. This information provides some explanation that I think will help you:
And this post also provides useful info:
Both are found under Forum Navigation, which has many other topics to help you!
w.r.t. your question: “Is there anyway to let the CPU take more of the strain.”
You’re not going to be able to “push” more GPU processing onto your CPU, such as getting the CPU to take up 50% of your GPU processing. In MSFS, both CPU & GPU (and to a lesser extent, memory, motherboard & drives) all need to work harmoniously to get the best performance (frames per second). Also, MSFS 2020 is main-thread limited, which means you’ll never see your i7-13700 running at anywhere near its full capacity.
In your situation, you have, as @MagicQuasar1176 points out, a CPU-GPU mismatch, where your CPU is over-spec’d for your GPU. You could certainly upgrade your GPU - knowing what motherboard you have would help in making specific recommendations. Also, how much memory do you have on your motherboard?
While spending £200 - £300 for a better GPU would improve performance - there are others who can probably suggest how much better, depending upon the model - you may find that your £200 - £300 would be better spent after the hardware specs for 2024 are released (date unknown at this point, though) if you are willing to wait until then.