I can see why the thinking is to develop in towns and cities where there's already the infrastructure, but you're right in that if planned poorly it can lead to big issues with not only overcrowding on public transportation, but also impacts on the grid, water and other utilities. Obviously things can be fixed if there's the will to invest - and not just take some S106 funding to do a few token projects here and there and cross your fingers.
Now we have the potential to build homes that can effectively operate off grid, by designing properties to utilise solar (possibly wind too, if you had large turbines to serve new build estates) along with mass battery storage, heat pumps (that could heat and cool), EVs meaning no pollution at point of use, and so on - why aren't we looking at building new towns and cities, and investing in transport links to serve them. Follow the garden city style concept to give people more space and land, rather than squeezing in huge tower blocks wherever there's space in a city to the point where the quality of life is deminished.
Of course, the people wanting to build aren't the people running buses, trains or roads, nor the people planning schools and hospitals. It's all very disorganised but is a topic in its own right that will never likely find a workable and logical solution.
The problem at the moment is a lot of the development is the complete opposite of all this. Just round my way, we have Henlow/Stondon/Henlow Camp (the place is such a featureless dump that no one actually knows what to call it), which every time I drive through there has sprung up a new development somewhere. Yet the “village”, if you can still call it that, has virtually zero facilities. Cue people jumping in their car and driving to places like nearby Hitchin, which itself doesn’t actually have that much in the way of services, think of hundreds of new homes and it isn’t difficult to see the priblems this causes.
Then there’s developments in much smaller villages. Every village near me has had new housing built, lots of it in many cases. Again, zero amenities - a village shop in some cases is about the sum-total. So now all the local lanes are choked with cars again driving to the nearest town for the slightest thing. Thanks to all this it’s very unpleasant cycling anywhere near me now except overnight, as pretty much every single road is way busier than 20 years ago.
Then there’s Stevenage. Already a pretty hideous town for the most part, to the extent where the town centre looks about as derelict as Pripyat. Massive new estate going up on the outskirts, formerly green fields much used by walkers. The town is already heavily congested, and the motorway can’t cope, Labour cancelled the plan to widen the motorway back in the 1990s.
There comes a point where we have to say that the land simply cannot take this, and housing has to be rationed just like any other scarce good or service - by the price system determined by the interaction of supply and demand. If people can’t afford to live in the area then they have to live elsewhere, simply as that, which in some cases may mean being unable to move here from abroad.
The whole Thameslink shambles is just one example of how the infrastructure can’t be made to cope. They’ve had 8 years to try and make it work, and if anything things are heading the wrong way.