It works the opposite way: cities operate on a zero-sum basis, especially when an MSA is declining in population the way many Rust belt cities are. Detroit may be the epicenter of the MSA but the other cities have all the incentive to see Detroit - and other cities - suffer so that they can maintain the engine of "flight to quality". Perhaps race is no longer the primary driver of this, as realtors cannot legally use race as reason to sell homes in the hinterlands, but the motion is decades in the making. Unless the Federal government gets involved (again), many US cities while barely function and their nearest and oldest suburbs will suffer a worse fate for not having the same level of infrastructure and sense of permanence to buttress them from sloppy decay (sorry that's a gin and tonic line).

New infrastructure is often vastly cheaper to build than existing infrastructure is to maintain and adapt. So, letting some city's die IMO has value.

DC is probably the classic example of a city best abandoned. We already moved capitals once, and frankly we would be well served by doing so again. DC was designed to be hard to move around in and guess what, it's hard to move around in.

Detroit, while not nearly as bad as some, really does not fit the needs of a modern population.

PS: It can literally be 10 times as expencive to build infrastructure in existing city's.

Indeed, Oakland County is a great example. It has happened elsewhere in the state of Michigan but not on as large a scale. When you look at Genesee county and the hole that is Flint with the its wealthier suburbs around it.