Curtius and poetry

I mentioned that I intended to read critics and biographers to keep me focused on poetry.  Unfortunately the more I learned about the various poets, the less I liked them (or their poetry).    So I just recently began seeking focus in literary history.  I decided to start with Curtius' European Literature and the Latin Middle Ages.  I barely got into the Introduction to the 2013 edition by Colin Burrow, when I encountered something I resisted:  Burrow wrote of Curtius, "His principal thesis is that the classical tradition spread and sustained itself through the study of rhetoric, and that the chief way in which that continuity was manifested was through the recurrence of 'topoi,' or rhetorical commonplaces.  These included notions that could be digested into a single phrase, such as the puer senex . . . "

Earlier Burrow quotes Curtius as believing that "A community of great authors throughout the centuries must be maintained if a kingdom of mind is to exist at all."   Will Curtius argue that writers ought to stick to the traditional topoi?  Would Harold Bloom agree that all of the writers in The Western Canon stuck to traditional topoi? 

Burrow writes toward the end of his introduction, "The Middle Ages described here are not at all dark.  they are effectively a long series of renaissances and enlightenments that run on until the eighteenth century, after which the real dark ages begin."  

I wonder what Curtius has in mind.  Have the topoi been expanded into poetic themes, literary genres?  And what does he mean when he writes (assuming Burrow is accurate) that our civilization entered the "real dark ages" after the eighteenth century?  Mathew Arnold's Philistines, Spengler's Decline of the West, Arnold Toynbee's Civilizational suicide?  All this is very provocative and I may be straying further from poetry than I intend, but . . .