I agree it's annoying when people make it hard for dogs to have a proper run in an off lead area. I do a lot of apologising and usually end up in some sort of conversation with them or introduce my dog to them, and they're usually ok with the occasional doggy interruption. My dog is a major groveller and her greeting antics are usually quite entertaining so we probably get away with more than someone with a Husky or other big dog might.
So I guess your best bet in a dog off lead area is to talk to people like that and find out what they're thinking - in a nice open minded way and let them meet your dog under supervision and see that it is friendly. It would also be an interesting challenge to train our dogs to give people like this a wide berth.
My favourite oval has a cricket pitch squatting in the middle of it which is off limits to dogs. Clearly it's the cricket pitch's fault for dogs running on it . My challenge is to persuade Frosty that jumping the rope or barriers and onto it is forbidden. Doesn't help that the grounds manager is fine with pitch invasions some days and not others depending on whether it's soft or not, so some days he pats her and some days he scolds her. I get a lot of exercise on the days when pitch is soft. "Frosty This Way"- me run away and sometimes hide.