If you ask the objective and measurable question of which neighborhoods tourists pay money to see, the answers are almost exclusively older neighborhoods,That doesn't sound like a good objective measure of what is a "nice" neighborhood -- I visit a lot of places as a tourist that I wouldn't want to live in. We have the neighborhoods we have because people are choosing to live in them.
Some things, like a central car free housing core with cars relegated to the outside edges of the neighborhood sounds attractive on paper (and for some people in real life too), but when you picture yourself schlepping groceries 2 blocks to your house, or walking the baby out in the rain to the car to take her to the doctor, it's less attractive for living, at least to those accustomed to living in the American car culture.
But really, it comes down to the bottom line -- people prefer to pay less than to pay more. If houses in a cookie cutter boring neighborhood cost 10% less than the ones in a planned neighborhood that's objectively nicer, it's going to be a lot harder to sell those expensive homes. So the developer's not going to build them in the first place.