I've tended to stop going as much lately because my dog finally has very reliable recall and I trust him in an unfenced area to stick around me. Before I would go to the dog park but be extra vigilant for exactly the same reasons OP mentioned. The breed has a reputation, anything my dog is involved in will probably be blamed on my dog, so I don't let him get involved in anything. He's extremely social and loves other dogs but he can get into dominance issues with other dogs and then I have to call him off or make sure he doesn't do anything.
For those of you with yards, with a pack of dogs, I don't see any reason to go to the dog park. But many of you don't think about the people living in cities, that might not have a lot of friends with dogs, and if they have friends with dogs they don't have anywhere fenced to let them play. So a dog park is a wonderful thing for them.
I think the more ignorant someone is, the better dog parks are for them. There are issues...but rarely is there a death or a bloody fight. I've actually never in 2.5 years of going to various dog parks seen any dog get seriously injured. There have been scrums, there have been fights, but I've actually never even seen blood get drawn from a dog. People around here are vigilant, don't want their dogs hurt, don't want to hurt other dogs, and so they don't allow it. A person that does bring an aggressive pooch usually gets quickly shunned and judged...and trust me they care when 20 people are looking at them funny and holding their dogs back. Or even saying things to them about their dog.
If we had a thread for each time a person went to the dog park and didn't have any issues, and just had a great time with their dog, those would out number the "I had a bad experience" threads by thousands.