When you argue for housing reform to legalize denser development in our cities, you quickly learn that some people hate density. Like, really hate density, with visceral disgust and contempt for any development pattern that involves buildings being tall or close together.
The walking is a non issue after a few weeks, you won’t even realize. I can’t remember the last weekday I didn’t get under 10k steps without doing any non essential walking. You’ll be much healthier for it.
Unless you’re in a wheelchair or on crutches in which case moving around a lot of Tokyo gets really ugly and taxis are both slow and quite expensive.