Just did a quick check and Fortnite is more cpu intensive than GPU. This means that your cpu will generally Be loaded up more than the gpu. So your gpu is having a walk in the park while your cpu is taking a dozen dogs out for a walk in the same park lol.
The utilization is okay, that's just how it works. The only thing that you should consider checking is the temps on the cpu, as long as it's in the safe range then you should not worry about anything. I would also consider checking core utilization while you're gaming, and see how many cores are actually being used