You're making a HUGE leap from "is not super inviting to pedestrians" to "does not function." And at any rate, this building is way more pedestrian-friendly than, say, the Old Post Office Building (or even the new one!).For all of human history, with the exception of the past 50-100 years, cities have been built on a pedestrian scale because there was no other option. In the 20th century we were able to ignore the pedestrian and focus on the car. This lead to some architectural movements that should be preserved, but are often hostile to a pedestrian city.
So we can view a city as a museum, or we can view it as a functioning city. Many places have the luxury of being built in a way that is functional so that preserving what is in place preserves a city that functions on a pedestrian scale. When we preserve this pedestrian hostile architecture in place we preserve a city that does not function.
Not every building needs street-level retail to be "functional."
And it would also destroy the artistic integrity of the structure.A simple Apple-style glass curtain wall between the four legs of the building would create an indoor space that could function all year round, with island-format retail or food vendors inside.