Urban planning is particularly difficult because there are so many factors to take into account.
Most of the time what is good for the individual, or at least what the individual prefers is not what's good for the group as a whole.
Like everyone wanting a backyard, but also to be close to the city center. This is why so many cities sprawl all over the place, making public transport a nightmare.
It would be better if people understood that you have to trade space for convenience sometimes.
It's a shame because cities often grow up on fertile land, since it attracts settlers and industry. So, when the city gets big, it takes over the fertile land, which is a waste.