Which game in particular? I would say definitely, the GTX 980 is a very powerful GPU, while the FX 6300 is a decent CPU, its single core performance, which is very important in gaming, is quite weak. To get the most out of that GTX 980, you might want to get a CPU with better single threaded performance, such as an Intel Core i5 (Sandy Bridge i5s are still excellent choices on a budget), or even a newer AMD Ryzen. If you are REALLY on a budget, you can overclock your CPU if your motherboard supports it, or look into upgrading to something like an FX 8320, which has 2 more cores. That being said, I would imagine that even at half usage, gaming performance should still be decent.
Well, if uyou play COD WWII and PUBG, those games are badly optimized in general, you won’t get good performance from any CPU you use. This is not necessarily your CPU’s fault, but I’m other games, the FX 6300 will definitely bottleneck your GTX 980.
COD WW2 is pushing my 4670k 4.3Ghz very hard, even with fps capped at 60 my cpu is running at near 100% across all 4 cores. My cpu is significantly stronger than the FX6300.
I couldn't find any good cpu benchmarks for COD WW2 but your FX6300 is a fair bit weaker than the minimum recommended AMD Ryzen 1400. Your FX just has very weak cores which upgrading to a FX8xxx isn't going to fix as it has the same weak cores. Without a good cpu benchmark I don't know if this game can utilise more than 6 cores (unlikely) and if it cannot upgrading to a FX8XXX will do next to nothing for you. Unfortunately you have a cpu based on a 7 year old design and its just not good enough for modern AAA gaming at 60fps.