Earlier quoted context omitted.
Denver still has the issue that it's a 20 mile drive from downtown out of some misguided belief that the city was just going to instantly grow out to it.
When you build an airport near the city, it becomes impossible to expand. San Diego is a good example of this, a single-runway airport that's surrounded by the bay, I-5, the Marine Corps Recruit Depot, and a residential neighborhood. It's running near capacity and impossible to expand. There's simply nowhere to go.
https://en.wikipedia.org/wiki/Category:Artificial_island_air...