Aurora R7, i5-8400 CPU bottleneck

I have an 8th gen i5 cpu, gtx 970, 16gb ram, stock fans, sata ssd and m.2, stock motherboard that's capped at i7-8700.

I always hear people saying the i5-8400 is a good CPU, which I would agree a couple years ago, but for most games it bottlenecks at 95-100% cpu usage. Games like: BdO,  Squad, Call of Duty modern warfare and cold war, Witcher 3. 

Mind, that it can run all these games just usually on some of the lowest settings. I know I'm a little limited on graphics settings because of old gpu but even if I were to upgrade that, correct me here if I'm wrong, but the cpu is still gonna be bottlenecking hard. 

On top of the cpu problems as I've looked into upgrading, I basically would need an entire new pc because of needing a new motherboard cpu gpu psu.

I've also heard that getting an i7 8th gen is really just not necessary for gaming really since you don't use or optimize the use of the additional cores.

Sidenote Upgrades List: I've added 8gb of ram from the stock, added a sata ssd and m.2 since I accidentally broke my HD that came with this while installing a gpu xD broke the pins on HD. and upgraded the amd 500 series to gtx 970.

so at this point I'm just about at the end of upgrades I can do on this thing without shelling out a ton a money for just marginal upgrades.

Any thoughts/recommendations for this? At this point I'm about ready to just get new case, motherboard, etc basically the whole thing. Since all the compatibility things are just so limited and a headache to keep track of for very marginal upgrades. Not to mention the size of the r7 case makes it so I can't really get a new mobo w/o getting a new case and the case og r7 case rgb and power buttons will get messed up with new PSU in addition to already maxing out the 400W or 450W PSU.