The whole concept of a suburb is because people needed to be close to cities, but diversity drove them from their city neighborhoods. A lot of people don't need to go to cities any more, and they are leaving the suburbs, which would relieve things a bit except for immigration.
The latest term is 15 minute cities.
From a city designer's point of view, it's easier to just lump everything in one place, and not every few miles like the suburbs require.
The whole concept of a suburb is because people needed to be close to cities, but diversity drove them from their city neighborhoods. A lot of people don't need to go to cities any more, and they are leaving the suburbs, which would relieve things a bit except for immigration.