I agree that our definitions of quality and value will be determined by our personal criteria, personal aesthetic, and individual frame of reference.
The term "trashy" is one I hesitate to employ regarding any literature, though it has its applications. (Maybe I wouldn't hesitate to apply the term to many romance novels...) Just because a book is written for entertainment and falls into the pulp/genre category doesn't mean that the book is trash or trashy.
There is often, however, a stark and immediate difference between literary texts and pulp texts. Pick out one paragraph from any part of any book, literary or genre/pulp, and you can usually tell what kind of a book it is. This is not strictly, 100% true, but I would guess it's 95% true. That tells us something about how different these types are and, to me, justifies the continued distinction drawn between one type and the other.
A question that we might ask to complicate the debate here is - Which is more worthwhile as a reading experience, bad literary fiction or good genre fiction?