Near where I live, there are plans to build 6500 new homes, with associated schools, hospitals, indistrial units and a science park. The homes are going on greenfield sites, the industry on brown. The floodplain area is going to be parkland. All fairly sensible.
The site is only 350 acres, so it's going to be a squeeze as usual, but I bet if the developers had twice the land, they would build twice the number of houses, not make each one bigger.
I'll say again - there needs to be some regulations covering minimum room dimensions. That is what will make a difference to the vast majority of people who can only afford one of these cookie-cutter estate houses.