More than 30 years ago, Dr. Ian Dunbar implemented the research by Scott & Fuller to expose dogs to the world while they were young, accommodating the fear cycles. He set up Sirius Classes, so that dogs wouldn't be fearful, bite strangers, and be released to the dog pound, where they would be euth'd in 3 days for being aggressive and dangerous. This was a common practice! There were few or no No-kill shelters at the time. He popularized the term, "socialization" and described the protocol, simplifying it for new owners ... owners who would release a puppy if it bit little Timmy. Everyone (including me) simplified Dunbar's method, so that new owners could get a start.
In the 1950s - early 1970s, dogs ran around the neighborhood, and didn't need this exposure. My retrievers were confident and well-adjusted. Great as pets and fine for hunting in the field and the marsh. Later, I adopted a GSD as a pet in the 1980's and kept him in the yard, as was the law, taking him for a walk twice a day. I couldn't understand why he wanted to eat every dog that he saw in the neighborhood, and why he barked at some strangers - "Fear aggression" wasn't a common term. A neighbor with lots of kids and two calm GSDs explained that I needed to socialize my dog ... when it was a puppy. So, 10 years later, when I got another retriever, I read Dunbar's method and implemented it, resulting in a well-trained, confident pet and therapy dog.
Yes, you can't just throw your dog into a dog park to learn about life today, but if you want to interact with people, "let her habituate to her world" in a 'controlled and supervised manner'. And, yes the meaning of the term, 'socialization' was diluted. In the comments, someone wrote that they call this process S. E. E. Which stands for Systematic Environmental Exposure. ... My eyes glazed over at this sesquipedalian phrase. ;-) Imagine trying to maintain the attention of a new owner.
And, there are over-generalizations in both directions. If you have a herding breed, you may not want broad exposure. A working dog, an agility dog, may not interact well. But, if you have a Retriever [or a Pit bull], these breeds were developed to interact with people, and you can run into trouble if you don't guide and reinforce this tendency. If you visit the K-9 units in larger cities, the ones that use positive reinforcement rather than aversion method for training, you can see some well-trained patrol and scent dogs, that come home as family pets, when they aren't working. With greater exposure to the environment, these dogs are more predictable, as Scott and Fuller described decades ago.
The Sirius method for socialization addresses the bullying aspect to interrupt and nip it in the bud early. Puppies learn to play nicely, learn bite inhibition, and may even learn to self-handicap. Puppies that have been supervised with a variety of other playmates will learn to take turns, and adapt to various play styles. While I agree with 2GSD4IPO that a well balanced dog should be fine if socialized outside that window [I did it with a 1.5yo dog!], how do you get a 'well-balanced' dog ... by gentle, supervised exposure to selected experiences. Although it sounds glib, a trainer experienced with the Sirius protocols can help.
Having said that, I am probably one of the 'offenders' who led
[email protected] down the wrong path about just exposing a dog to 100 different dogs, people, and experiences without guidance for specific supervision and training, also. Even in socializing my own dog, he is still scared of the Vet's high table for examination (she has to look at my 80lb dog while he's standing on the floor). Although he will ignore most barking dogs, there are some dogs that still threaten him. And, he barks at people and dogs through the window, although it is no longer out of fear. Still a work in progress.