The earlier audiences were very specialized. Who, really, would care about referring to a cup from the Thespian well Either family or close friends of Sir George Sidney or people who knew what "Thespian" meant. Likewise, in Virtue, the ordinary person can understand what the poet meant by the whole world turning to coal. A hundred years later more of the potential audience "got it."
The reason that Gulliver's travels was so popular was that more people saw it as satire and not a clumsy fairy tale. The author refers to Care and Vigilance, somehow used in order to protect one's belongings from thieves. This would probably mean something to an audience in 1726 than it might have meant a century earlier. Jane Austin also developed women readers who may never have heard of Ben Jonson.
The thematic change between these two centuries can also quite simplistically, be related to the boutique and department store analogies. While the early poets and writers had a limited audience (with boutique audiences looking for something fine and special) the next century produced more of a mass-product that appealed to a larger audience.
John Donne's "Mistress Going to Bed" is, to use a rather unflattering word, "precious." In the middle of the Seventeenth century, thematic change can be seen in Milton, who on the other hand, creates a wide and fundamentally moral canvas with a nation that survived the rift between the new Angli ...