Here in the Netherlands, we have a huge population density. About 50 years ago, we created a shit-ton of land (Flevoland) and plopped down some cities. Those cities kind of worked out, but there is very little life there. They mostly function as suburbs, where people live but don't work.

More recently, in the north we tried placing new cities, turns out that people don't go and live somewhere if there isn't work, and there isn't much work in the north. Those cities are now failures. Heck, the big established cities in the north are being drained by people moving towards the cities in the middle.

Cities grow organically because people want to live in that city.