There are positive physical and mental change that happen with more intensive cardio and with resistance training that you can't get from walking no matter how much you walk. And there's nothing herculian about those modes of exercise.
The danger of hyper-optimization is people just giving up altogether. That's why a lot of those intense diets don't work.
Does Keto work? Yes. But does it actually? No. Because being on Keto is very, very hard and people just give up. The vast majority of people who start Keto will not stick to it.
But switching out soda for diet soda is easy. So, if I'm inclined to give suggestions, I'd rather suggest that.
I'm talking about the basics. For anyone who wants to get benefit from exercise. If you think you're getting those benefits in some other way, you're lying to yourself or you don't understand what we're talking about.
But, for most Americans, they need to be walking. The rest can come later. Sorry superman.
I am also saying that for those new to the gym, starting with say 10-20 minutes every day is better in the long run than 1-1.5 hours three times a week before the body is acclimated or before proper form is developed. This lowers the risk of injury that could set back the health improvement endeavor.