>You can read scrolling movie credits just fine at 24 FPS
Honestly I actually struggle with that. But working and gaming at 60hz is still perfectly fine with me. I even purposely run my Valve Index VR headset at 90hz instead of 120hz because I don't need the extra frames
You can't play a game at 15 FPS. It's a moving slideshow. And it was never fun. 30 fps looks pretty bad, and even 60 fps is decently choppy. I'm not sure what your exact point is, but once you try 144hz or higher, you'll never, ever, go back.