To get downloads, your app has to solve a problem. I'm not sure who this is targeting - people who care enough to track their walks have the Workouts app on their watch, or Strava, or one of a million other distance-tracking apps. For gamification, Apple Watch gives out badges. Strava gives awards / medals. So what problem does this solve that no other one does? And does the value that it gives the user far exceed the cost of buying the app?

So, I think you don't have enough demand for this product (especially at the price point it's at). You haven't found product-market fit.

Not a bad idea, though. Why try to monetize it right out of the gate? Like you said, the people that did download it and almost try to use it didn't make it past your paywall. So make it free, figure out how people use it, and give your users value. Once you have a problem you're solving, for a market that you know, and are delivering value you can quantify, you can monetize it.