There are many reasons why dog parks are a vital part of any dogs development. Some sites will attempt to scare people into not using them, however these companies are mostly ones that will financially profit from you using their services instead.
One of the prime reasons given is that the trainer has fear that a dog will not make you the alpha dog, that it will listen more to any other dog in the park. It is clear that these so called trainers have spent little time in the real world or in fact dog parks.
There initial claims are that it is important not to have dogs exposed to off lead dog parks for the first year plus of their life. THIS IS COMPLETELY OPPOSITE OF what will create a well socialized dog!
The naive fear is that a dog will be so smitten with anyone else that it will immediately abandon its owner. Perhaps this is possible if the owner spends no time with their dog or gives the dog little stimulation or training and reward. However anyone with the simplest knowledge of dogs will know that the first 3 to 6 months are absolutely vital for a dog learning socialisation skills.
The dog has just left its mother and siblings and is looking for new guidance. As it grows it must still know what its boundaries are, and how to play well. After all, play is the way that they gauge their position in the pack, almost the only reason that they play.
The bond between owner and dog is very easy to establish, if the owner is going to become a good owner, that is take their dog to off lead dog parks. The owner will be continuously involved in their dogs development and the off lead dog park will just be another tool they use.
For those with an over developed fear complex (thank you trainers, you know who you are) there is always the on-lead walk training sessions. It is true that these are very useful in the dogs first year. On lead walking will bond the dog with you, if you do it right, and will exercise them, get them use to many strange and exciting sounds like traffic, and may help with recall. BUT it does nothing for socialisation and making a dog friendly and confident.
How much a puppy or adult dog bonds with you depends on the time you put in, and the level of walking, discipline and affection you give it. As most people who have had puppies know, they seem to have a limitless amount of energy that needs to be used so they can sleep well at home when you go to work. It will decrease separation anxiety and prevent boredom.
How will your dog get that by simply walking next to you?
How will the dog learn an acceptable level of play or how hard to puppy mouth other dogs, which dogs to approach etc?
Social dogs give puppies and older dogs a lot of latitude in how they behave. They understand that puppies are learning and may try and over play, and as long as the puppy doesn’t bite them hard, the puppy and owner should have no fear of any interaction.