I think that's generalization, to be honest. The parent comment's intended (I believe) use of "car culture" implies anything that encompasses cars. When I wrote "how they're used and how the automobile infrastructure (roads/highways/etc.) is constructed", it was with respect to that parent comment's context.
In reality there are more purposes to cars. We shouldn't therefore apply some aspects of cars to the broad meaning of car culture.
No, I believe that they're talking about the ubiquitous need of a car for any given task. It would be nice if areas were designed such that a vehicle wasn't required to do more or less anything, be it restaurants, entertainment, general shopping, etc.
I'm not really sure what you mean by "We shouldn't therefore apply some aspects of cars to the broad meaning of car culture." It sounds like simply semantics at this point, that is, you infer a different meaning of "car culture" than the OP presents, but I don't feel that detracts from the point about the constructed necessity of cars.
In reality there are more purposes to cars. We shouldn't therefore apply some aspects of cars to the broad meaning of car culture.