In the end does it really matter? I don't understand why AMD and Intel are so focused on gaming performance in the first place. Is any modern midrange CPU or better really handicapping gaming performance? Will any typical gamer be able to tell the difference between a 10600 and a 7950x in a blind test? It's not the old days where we were trying to reach a steady 30fps. When you're going from 330 to 355 fps it just doesn't seem to matter.
Thry are so focused on it because, without offence to anyone here, many tend to just look at numbers. Higher number = better, no matter if the difference is 1 FPS or 100, or if the difference dwindles under RL conditions where not everyone uses a 3090Ti and plays at 1080p or 720p where you actually stand a chance to see a difference. Gaming is also what the biggest part of non-professional customers use their machines for. What does your average Joe/Jane playing video games on their computer 3h in the evening care for more; (theoretical) gaming performance or performance in, let's say, Blender or Adobe Lightroom? Sure, some people have other hobbies like casual video editing or music production they use their computers for. But those aren't the majority. The majority are gamers of all ages and budgets. So that's where the marketing is aimed at.
You are 100% correct that it doesn't matter at all which modern CPU you pick for your gaming-only rig, and in all fairness, even the longevity angle is only really an angle when you are environmentally conscious and want to avoid e-waste (and even then, recycling into other systems or reselling is always an option). Let's say you buy a 12100 today with a decent B660 board, and let's say it lasts you two or three years. We now buy a 12700k instead with a Z690 board because that is what people realistically do with these chips, let's say that one lasts you four or five years, or even six. The 12100 costs $100 plus 120 for the board (or less if you are fine with a H610), the 12700K costs $400 plus minimum 200 for the board unless you are fine with losing the OC capabilities. What is the better value, and if you only gamed, watched video etc, and nothing more, did it really make sense to get the 12700K? Flip that around to AMD, same thing. High-end chips only make really sense if you a) expect them to last much longer than those six years mentioned above, or b) you do other stuff with the machine, too, like code compiling, video editing etc, that profits more from a better CPU. That gets even more pronounced at higher resolutions. And yes, this also applies to 3D cache chips.