I don't think you're saying the same thing.

Transportation allows people to live far from where they work, but that's everything from horses to bullet trains.

Free roads allow for dispersed uses but doesn't affect how dense of segregated they are. Beyond the cost and space requirements to park everyone's cars. Zoning is doing almost all the work you're describing - even with the presence of cars and subsidized highways, the built environment would look very different without zoning and with more market forces.