CPU Upgrade Advice

see the thing that is bothering me is that when I am playing Destiny 2, which my CPU should be good enough to handle it stays at 100%, which I am not a fan of, I am not even playing on like high resource intensive settings. Now, it could obviously just be D2’s fault, so it’s not a solid reason, but I have seen one or two games that need i7 4790 as recommended by “Can you run it”, and also I plan to upgrade my entire PC over time, so I want to start with the CPU since I have been saving up for like half the year now. So again, don’t pay any attention to the RAM and GPU right now, I will upgrade that later.