If the Canterbury Tales taught me anything, it's that medieval people could actually get pretty creative and irreverent when it came to things they cared about. It's the institutions and the background assumptions that are different. Individual people often weren't all that dogmatic, and indeed enforcement of societal norms was weaker in a lot of ways than it is now; but above the individual level, almost every organization was narrowly focused on the status quo or on zero- or negative-sum games. There was nothing forward-looking in the way that science is, or even in the way that serious utopian politics is.

(It also taught me that fart jokes are perennial. A lot of those scenes wouldn't have been out of place in South Park.)