They are wrong. I’m running a 3700x (PBO on) and a 3080. I predominantly game at 1440p but occasionally I will hook up the TV and game at 4K. Less gpu demanding games will always be cpu limited but more demanding AAA games are fine. Take Cold War for example, I run max settings at 1440p with balanced DLSS and RT off. I get 150-180 FPS average depending on the map. The cpu uses 12 threads but all stay around or under 75% usage. At 1440p I probably would get a handful of extra frames with a 5600x/5800x. At 4K the cpu becomes less important.
I have assumed you will have fast RAM. I’m running my 3200mhz CL16 overclocked to 3600mhz CL16.