I don't think its possible to find much fault with the older Trek steel frames. They were built as good if not better than many high end Italian/French bikes. Although they lack the reputation and history of the foreign makers .......... they ride like a dream.
Its to bad Trek alienated the steel frame market ........ but then they wouldn't be the "empire" they are today if they hadn't.
Any mid to high end Trek in good shape is worth hanging onto in my opinion. I love mine.