It's frightening how completely disconnected from the real world this is.

The world is full of people who aren’t realizing their potential in large part
because their cities don't provide the opportunities and living conditions
necessary for success.

No, the world is full of people not realizing their potential largely because most people just don't. Whether it's just that someone is not motivated to do more than is necessary, or the real social problems that affect people all around the world, in both cities and suburban communities.

• The guy serving you your hamburger isn't realizing his full potential because he grew up in a lower-middle class family who didn't encourage him to do well in school or go to college, he grew content with his boring life hanging out with his friends and working paycheck to paycheck, and he honestly has no good reason to try to achieve more.

• The single mother with the two kids and a heroin addiction isn't realizing her potential because when her high-school sweetheart husband left her she had trouble getting a job, so generations of misogyny & patriarchy convinced her she can only turn to stripping to pay the bills, got hooked on drugs and alcohol, and is now locked into a slow circling of the drain.

• The young black man in prison isn't realizing his potential because generations ago the systemic racism of our country pushed his family into a tightly impoverished community with no businesses, no access to transportation, almost no education, no access to family planning, and rampant drug and alcohol abuse, which the country then took advantage of by creating for-profit prisons and mandatory minimum sentences to convert most of the people in his community into a series of bad choices which only result in debt, incarceration, teen pregnancy, drug addiction, and crime as a survival tactic.

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A high leverage way to improve our world is to unleash this massive potential
by making better cities.

I've lived in cities most of my life. Their problems are not engineering problems, they are social problems. You can't "unleash potential" without first convincing the people who live there to vote for it, work hard for the change, and of course pay more tax money for it.

• Why do we have too much traffic congestion and not enough parking?

○ Because the city - and its residents and taxpayers - refuse to pay for better public transportation.

• Why do cities not have better transportation?

○ Because politicians [and voters] fight over how to spend what little tax revenue they collect.

• Why don't the residents pay more tax money to fix the problems in their city?

○ Because a combination of high unemployment and low wages due to a concentration of wealth and corporate power refusing to raise wages while profits have skyrocketed have left citizens with very little left over money. Food and housing comes before transportation taxes.

• Why do cities not have affordable housing?

○ Because rich white people don't want to live next to poor black people.

• Why isn't there a diverse range of people living and working in cities?

○ Because first you have to create economic and social equality for a diverse range of people and grow an actual population thereof, rather than pockets of socioeconomically disadvantaged minority groups.

• Why aren't cities constantly evolving?

○ Because some are able to successfully resist housing price inflation and gentrification, while others have a stagnant economy, and others are simply consistent in their status quo.

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If you need to make a better city to realize your potential (which is stupid, since we were still realizing our potential before we had "great" cities), you first need to solve your social and economic problems before the city can be better. But this is a boring, depressing, non-"startupy" answer, so never mind me.