You can't ignore the factor of the automobile in the end of the front porch. Historical communitarian impulses ended well after the disappearance of the large front porch, but the adoption of the car and the architectural shift are almost simultaneous. Living in an older house with a large front porch on a two-lane tertiary arterial made the cause immensely clear: even the moderate traffic of a residential street makes a front porch wholly unpleasant. The noise, the smell, the dirt from the vehicles, the unsettling speed of this modern form of transportation, the post-automobile danger of the street to children - all of these things helped ruin the front porch and yard. And by the late 1920s, domestic architecture shifted to accommodate this new reality, moving the relaxation space, the play space, the functional outdoor space, all of it, behind the shield of the home.Interestingly, our current house, being on a dead-end street off a dead-end street, has the only large front porch in the neighbourhood. And we actually use it, in the summer, rather more than we use the little patio - tho' being the only such house, we have no one with whom to be social.
Oh, and if you don't think automobile speed is unsettling to someone not in an automobile, try walking on a sidewalk directly next to a traffic lane sometime, particularly on a busy road. The demonstrated, studied reality is that almost no one will use a sidewalk in that state, regardless of the actual safety situation, unless they have no other option; there must be a perceived barrier, even if that barrier provides no actual protection, to provide a sense of separation from those giant roaring running animals your lizard brain sees stampeding by you. A row of parked vehicles does nicely; so does a planting strip. Sidewalks built without these on streets of any speed or traffic load are all but a complete waste of money.* Sidewalks built with these considerations get used.
So given all that, it seems obvious that in an automobile era, front porches were simply doomed. In that, I think the second article places the cart, as it were, before the horse; it does mention the automobile, but places the dependency on the car as a result, not a cause, of the loss of the front porch - and, following that, the loss of local community the author is attempting to describe.
*: They do provide some value in the sense of an emergency pedestrian path in event of, say, automobile breakdown.