I actually very strongly disagree. Walking is maybe one of the most underrated tools for exercise, for several reasons:
- it's extremely low fatiguing and low risk of injury, perhaps the lowest of any form of cardio outside of an elliptical or swimming
- Unlike either of those though you can walk anywhere, and you can insert it into your daily routine. Walk to work, walk at lunch, walk to the gym
- Because we're such practised and efficient walkers you can walk while you're on the phone, listening to a podcast, etc.
- Because of all of this you can get in your low intensity cardio without disrupting your training or life routine
You could certainly burn more calories in less time if you ran or did some form of HIIT, but with the barest amount of conditioning you could get to a place where you could walk for hours and hours with little to no problem. The upward trend of calorie burning is basically endless with walking, because the fatigue always remains incredibly low.