Loose lead walking is in my opinion one of the hardest things to master. Why? Consistency.
If you have to get from A to B in a hurry and let all your training go out the window letting your dog pull the whole way then guess what- they have been massively rewarded by walking forward the whole time, pulling you along to get to the destination. I have a little trick to get around this which will help massively. Loose lead walking for me is precisely that- walking with a loose lead. I do not expect the perfect obedience standard heel position. Most dog owners simply want to be able to walk down the street without getting their shoulder pulled out the socket!