If idk, all car companies came together, pooled their resources and knowledge and created joint car lines, using standardized optimized production lines across all of them, resulting in only one line of car per use case (one large truck, one small truck, a 2 person car, a 4 person car, a family car, etc etc) then no advertisement would be necessary. They could make the prices as low as possible to cover costs while still allowing some research into better technology. Everyone would just know/be able to find out “oh if I want a car I go to these people” and then you just choose the car that fits you, there’s no advertisement necessary because there’s no alternatives.

Of course, that doesn’t work because people are shitty, it would be a monopoly and the monopoly would jack prices up to infinity, the quality would be as bad as possible, resulting in an incredibly bad product for incredibly bad value.

You are basically talking about a socialist or communist ecenomy, and there are good reasons that that is a horrible idea for certain industries (and a good one for others, and an even better one with some kind of bastardized hybrid system like the chip industry in Taiwan).

There is no best system, IMO everything should be evaluated a la carte instead of trying to centralize or privatize things ideologically.

Many private organizations that get like this are like the worst of both worlds though, where they lose the entrepreneurial spirit, efficiency and drive without any of the "benevolent" motivations and restrictions of a centralized system, especially when they get rich enough to push back against ethics.