Re: We have the technology
"The bigger problem with mega cities is they are just too 'ing dense. Most people don't want to live in them so they find a house or flat in the burbs and commute."
Those are the second and third order problems. The first order problem is that they're too big in terms of both population and the volume of business being conducted in them. Distribute the business to smaller cities which need a smaller population, less density and less commuting.
There may, of course, be a zero order problem of too many people but we seem well overdue for a pandemic which could take care of that.