I'll be one of the odd balls out, I know. I really like the dog park. Tali, also REALLY loves it there.
But.
There are risks. You have to know that going in and make your own call.
I think one large part of "bad parks" is some of them really are, just a small open field with a chain fence. I may be wrong. Theres a few of these in my city, and I avoid them at all costs. Too small, too many dogs in a small area. If your dog and you don't have a lot of room to maneuver/get away from a hazzard - thats a very bad thing.
Theres 3 very good parks in my city. One is only 5-7 minute drive, that I goto every day.
Panamoramic picture of about 1/6th of the area.
The park is huge. Even when busy, tonnes of room.
Size isnt the only problem of course, people/strangers and their unkown dogs are there too. However, size helps you avoid most encounters if you don't get a good vibe from them. The whole "velcro dog" with Tali comes in very nice this way. She will only go about 50-75 feet away from me most times, so if I see a dog i'm unsure of coming towards us, I can go another direction and she will follow.
Of course observation is your best key. Reading other dogs in the distance you've never seen, how they interact with the environment around them - all tools you need to have with you to determine "Maybe i'll go this way instead".
Large packs are a bad idea too, typically 3 dogs is usually the most I want around Tali at once (Assuming those 3 dogs are not part of one pack). If more run over to us, i'll usually start walking away.
As for rough play - Yup tali does that. She's good about doing it with dogs her size or bigger though. Tali's a neck-biter/pinner with some dogs, but she knows when to stop. If another dog whines/crys at all from it - she hops off them. This type of play I usually either inform the other owner when it starts to pick up, or see what their reaction is like. I know a lot of people are not used to seeing their dog pinned down by the neck - so I make sure to stop tali from doing it, inform them, and if they seem reluctant about it, we leave them.
Now, with all that said - Things still can go wrong. I've had 2 dogs storm after tali when she went to go greet them, snapping like hell and not letting the chase off. One time I started moving toward the dog as they did this and the dog charged at me, giving tali time to get away from him. I then calm backed away, not staring at the dog and eventually the dog turned and went back to its owner. The reality is, you have to be ready to do these types of things.
I'm fortunate that the parks I frequent MOSTLY have responsible owners and are interactive with whats happening rather then just standing chatting and loosing focus on the dogs around them. Thats not the case everywhere though.
Best of luck!