I am so with Tracy on this. We used to have a pure GSD female and a male mix. Brought them to dog park all the time. When the GSD was about 9 months she was herded and bitten chasing her ball by an Austrailian Shepherd. Ruined her, as it made her very dog aggressive from then on. At the time I did not put it together. But made her very unpredictable around other dogs - she would bite first!
Those dogs have since passed and now I have a new pup Udo who is about 5 months old. Dog park? No way. Having spent the last two months in very focused obedeince training, with very encouraging results, one look at the chaos and mayhem going on at Dog Park is enough to turn me away immediately: Dogs that have been cooped up all day while their owners are at work, owners who "release" their dogs, while they sit around and BS, as their dogs "get exercise". A total joke.
That said, back in the day, we really enjoyed it - watching the packs assemble, bob and weave, even the big "all in a line" circle chases. But, there were often incidents. For me personally, after one gets a handle on some genuine training (come command, leave it. blind sits/down stays, and a good off lead heal) - which I did not with my first two GSDS - one sees what is going on at Dog Park and you really can't believe you let your dog simply "go" for that kind of experience. Our GSDs can just rise to such an immensely higher and rewarding level.
I think it is a personal thing, and there is no value judgement, as we used to love to go. I guess, I have just seen and experienced different realities that makes it "not right" for us any longer. Will we socialize and let our dog play with other dogs in a controled social environment, sure! That's part of being a dog. Will we toss them in the dog park chaos? No way. He is going to be too big and too dominantly minded to risk tweaking. And one bad incident at dog park can and will imprint the dog in very powerful ways. Just not worth it.