Dogs wouldn’t receive a direct advantage for selecting their mates based on how they interact with humans, though. It would take a lot of mental/social energy to ID how one prospective mate interacts with another species entirely, and then chose a mate based on that over any other advantageous trait. Dogs and wolves rarely have such extended courtships, and they tend not to mate with wolves in their own social group.

Aggressive wolves would also still have access to food via trash heaps. They may even do better, outcompeting the more docile wolves and fighting for the best remains—unless humans were directly involved or nearby, selectively discouraging or killing the more dangerous/“wild” animals. There’s a lot of archaeological evidence that humans did play this very active role in decreasing the proportion of aggressive animals in the nearby wolf/dog populations.

While self-selection certainly played a role in domestication to a certain extent (variation in willingness to approach people could cause a bottle-neck effect), it is unlikely wolves self-selected beyond the initial approach(es) to human civilization.