Not sure what the phrase "overly orthodox" means, but it is what is used in a new book on evangelization to describe a certain cross-cut of the Church. Unfortunately, if an author dismisses those who strive to be orthodox Catholics in a book about evangelizing young adults, the aforementioned author just lost his balance on writing a book for that audience. Speak to them, not down to them.
Certainly young adults can seem to go too far in emphasizing certain areas of the faith to the detriment of others. But, it is not for a lack of zeal, faith or love. But, rather it seems that the young adults haven't properly discerned how to handle certain situations.
For example, many young people (I have been known to do the same in my younger years) get very excited about apologetics and then try to use it to beat up others with great arguments for the faith. But, they do so out of a passion for Christ and a mis-placed understanding of sharing the faith. They don't need to be told that they are wrong for wanting to spread the Gospel, rather they need to be guided in how to be more effective witnesses to Christ's truth in the Church.
It seems that anyone who would condemn young adults for being "overly orthodox" (and them dismiss them because of it), doesn't have a very good sense of what it means to be a young adult in the Catholic Church today, nor how to reach them.