A well trained dog is a good dog. It’s a well known phrase but it does not mean that a badly trained dog is a bad dog. If the badly trained dog got some good training then it could become a wonderfully well behaved dog.
There are some exceptions but mostly a dog reflects the way the owner treats and trains it. If the dog owner doesn’t care then the dog will never know what the right thing to do is. Dogs need to be told what to do since they are pack animals and always follow a leader. That leader is you as the dog owner. So train your dog the right way to behave and you will both be happier.