Poor mobility for cars also translates to increased cost of living.
Nope, that’s backwards. Poor mobility for cars comes from higher-density development, which is also efficient development because you don’t have to spend huge amounts of money building parking. Getting rid of the cars is the thing that lowers the costs!
Futhermore, getting rid of the cars is also the thing that enables walking/biking/transit to be viable (because there’s physically less distance to cover, since you don’t have to cross a wasteland of pavement), which also lowers cost of living.
The bottom line is that if you build to accommodate cars, you will never have walkability. It’s geometrically impossible.
When you reduce the throughput of those areas, traffic gets distributed onto more roads. The result is that cyclists and pedestrians are less able to avoid cars with strategic route planning.
Distributing traffic onto more (uniformly-slow) streets means that cyclists and pedestrians have less need to avoid cars with strategic route planning because slow-moving cars aren’t nearly as much of a danger to begin with.