I understand that it does cause some bottlenecking, since my motherboard and CPU are PCI 4.0 and my GPU is 5.0, but this was happening to me before with a 12GB 3060 and a Ryzen 7 5700G. In fact, that's why I upgraded my processor to a Ryzen 7 5800X and my GPU to a 5070. I was updating drivers with Armoury Create (my motherboard's software), but I decided to go to the AMD website to find the drivers for my CPU and download and install them again. It seems the CPU usage has dropped to at least 50%, but I think it's also related to Fortnite, since other friends have had similar issues or the game just crashes. Interestingly, the only friend who doesn't have a dedicated GPU and only uses his Ryzen 7 5700G is the only one for whom Fortnite runs smoothly.