The big problem with expecting a city to be "100% walkable" is the fact that it's a goal orthogonal to conveniences like modern-sized grocery stores and big-box stores.
A big grocery store like Publix or Kroger needs about 50,000 weekly customers to be financially viable. Packing 50,000 people into an area small enough for them all to be within walking distance is hard. The one possible loophole to this rule is, if the developer of a large condominium strikes a deal with a grocery chain like Publix to allow the store's customers to park in the garage for free (along with guests of the condo residents), it MIGHT be able to pull off combining a grocery store and large parking garage with skyscraper on top (so it can be marketed to condo residents as a super-convenient ultra-desirable amenity, yet still tap shoppers who live further away).
A store like Target or Best Buy needs a MINIMUM of 250,000-300,000 customers within local-market range before they'll even CONSIDER opening a store in the area. Short of surrounding the store with an ocean of 50+ story skyscrapers, it's damn-near impossible to pack enough people into a small area to make a store like that economically-viable from pedestrian shoppers alone.
Complicating matters further, there's a middle ground where NEITHER big-box stores + dense residential development are mutually-viable. If the store's parking is free while adjacent buildings charge for parking, it will find itself in an endless losing battle to keep people visiting adjacent buildings from parking there. If the store charges to park in its own garage, people who live a half-mile away won't shop there, and will drive 5-10 miles to a store where they can park for free instead.
The only reason stores like Walmart can build a superstore in the middle of (relative) nowhere and survive is because it basically wipes out almost every other store within 10-20 miles, and draws customers from up to 50-100 miles away.
For years, Miami's planning department operated under the delusion that "ground level retail" was some magic panacea. What really ended up happening: building owners demanded rents they considered proper for a big city, and the storefronts remained perpetually vacant (or opened, then went out business within a few months). The fact is, there's actually NOT a lot of market demand for small retail spaces devoid of free parking below condos that are owned mostly as vacation homes and spend most of their time unoccupied.