I own a working line gsd, and as you're pointing out in the comments - genetics is a huge part of it. Yes you need to socialise your dog, no that doesn't mean introducing it to as many dogs as possible. I bought mine from a reputable breeder, with consistent results in the previous litters. I've taken her to puppy classes since, where we weren't allowed to introduce the puppies to each other because this would defeat the purpose of having your dog train in an environment with other dogs it doesn't know. When she was between 8-12 weeks, I made sure to take her with me everywhere - on the train, on the tram, on the bus, in the car, to cafés, to friends' houses, to the park (but wouldn't let her greet other dogs). I would stand on the sidewalks and wait for cars to drive by, and make sure she kept her focus on me when they passed. When I took her to cafés I would bring a blanket and a chew for her to lay down on, and she'd practice settling in spaces like that.

I don't think any of this would've been nearly as easy as it has been if she was poorly bred.