Could you do what you did in the video, but with your foot cut by a lodged glass, or relatively tired with a sedentary character? in a save that looks incredibly promising?
For me, what makes the game scary are those moments, not zombies that are naturally slower than a human being who is well rested, fed and healthy.
Why don't you try playing in sandbox mode, with the zombies that are runners? I am very afraid of them ...