If there was one thing I could change about Chicago (or an big city) it would be to create more car free zones, more zones open only to public transport, human powered transport, foot traffic. It would significantly lower the craziness of the streets while improving the air quality and, I feel, the sense of aesthetics of those stately buildings towering over cars.
In parts of Europe I have experienced cities where car traffic is minimal because of excellent public transportation (and the insanely high costs of owning and fueling personal cars). The cities felt more homey. The people were much more fit from all the walking.
In Chicago this would require vastly improved public transportation and a radical mind shift in the people that cars are a privilege and not a right. Not sure if any of our politicians would be willing to weather the storm of telling people that can’t driver their cars whenever and wherever they want.