Dogs can learn at any age. Sure it's easier to 'imprint' and develop a young dog, sometimes that's the scary bit when we start with a puppy. They are more than willing to learn and adopt 'everything' good and bad, right and wrong.
A confident, content well-mannered sociable dog is generally at the heart of what we all want from a companion dog.
Let's remember that a dog is always going to be a dog - we can't make them human. They are far less complicated and far more adaptable than we are. Oh yes, they are...