Key point: all of these "low cost, low effort" ways depend on people staying where they have influence. Any change to zoning laws, or to approve funding for bike and public-transit infrastructure, etc., requires residents who support those things. People who grew up in a city because that's where their parents lived, or who run away from the suburbs to the cities (or to other countries), have zero influence over the problem where it exists and therefore have little moral standing in these debates. Don't just make things better for yourself. Don't be a coward. Stand and fight.