[Terr_]

I think you've misread the parent poster.

* Their "not owning" means a swap to a subscription/license for the car, which could still be exclusive rather than shared.

* Your "not owning" assumes a reduction in the number of cars per capita.

In other words, the "dystopia" they are referring to is one that still has today's problems of gridlock, land use, urban planning, etc., with new kinds of problems layered on. Cars not being user-repairable, being nickel-and-dimed on features, a monopolistic used-parts market, and a general shift towards whatever boosts the car-manufacturer's profit margin.