In NYC you certainly could. It takes banning cars for personal transport and expand the subway. The city would improve tremendously. Not quite like waving a wand, but doesn't require tearing down and rebuilding either.
Public transport is ridiculously inefficient when you have to buy more than you can carry or have babies or toddlers or young kids. I suppose we should just eliminate kids as well in order to make the perfect urban utopia?
And what about when it’s 10 degrees in NYC? Walking on freezing streets to stations blocks away isn’t too fun.