Certainly Vietnam depends on tourism heavily. Yet they also have numerous other crops and exports (including coffee, rubber, shoes, cat fish, and milled rice paddy). In the last ten to twenty years, many families have gone from poverty to adding additions onto their homes. Local business in many cities is flourishing around tourism for both foreigners and local Vietnamese who never had the opportunity to travel before.
Has Vietnam lost its authenticity? Have they been altered by the outside world, shaping themselves to sell more tour packages? Perhaps. It is a country that is constantly changing and currently experiencing a level of economic growth only surpassed by China. Therefore, I guess it depends on your definition of authenticity. This is the true Vietnam. I have found the story I was searching for.