As strong as a current RTX is, it's only real purpose is 4k either 60Hz or 144Hz. Neither one poses a serious challenge to the cpu.
Cpu sets the fps limits, it's upto the gpu to live upto them according to details and resolution. So if the game allows a cpu to set a 100fps limit and you swamp the gpu in settings and resolution and end up with 50fps, that's all on the gpu. Dropping the settings and resolution to allow the gpu to hit 200fps, isn't going to raise the cpu set limits, you'll still only get 100. That doesn't mean the cpu is a bottleneck, it just means the gpu is overpowering a reasonable limit by not doing much of anything. OC, stronger cpus, game optimizations etc might raise that limit, but not the gpu.
A bottleneck is a component that slows down the flow of info from source to monitor. The cpu doesn't slow the flow, ever, it sets the flow limits. Ram, hdds can be bottlenecks, as can the gpu as all can choke the flow, lowering it below the limit set by the cpu. Games themselves and the engines, optimizations, scripts and code can be bottlenecks as well, but not the cpu.