Between Trent and Vatican II you had slow, organic, incremental change to mostly the rubrics. Some examples from the 20th century were seen with the introduction of the 1962 Missal, in which the 2nd Confiteor was removed, the altar candles were lit based on whether the Mass was a Low or High Mass (instead of the rank of the feast as is was done before), the celebrant and servers were no longer to turn toward the tabernacle when bowing their heads at the conclusion of the collects, the communion candle was removed, the readings could be said in the vernacular during Low Mass, the total number of commemorations allowed during any Mass was reduced to two (a welcome change in my opinion!), the order of precedence of feasts within a rank was altered to yield to more Feasts of the Lord and Sundays, among others. The 500 years prior to that I’m sure there were loads of other small, hardly noticeable changes.