To expand on my meaning of my original post, one can tell how DT's approach has changed because of how less proggy their instrumentals are. Comparing a song like "Learning to Live", "Voices", "Lines in the Sand", or "Trial of Tears" instrumentally to "The Dark Eternal Night", "A Nightmare to Remember", it becomes really evident in the way things have changed. There isn't the same buildup and release, the same sense of tension and swell, as before. Instead, there's a series of interchangeable riffs that do little, in my mind, to capture the audience's attention or draw them in.
In fact, I don't think it's wholly unsurprising that the few songs that I think hold these qualities off of the more recent albums ("In the Name of God", "Octavarium", and "In the Presence of Enemies Pt. 1") are usually held among the best DT have written in the past decade.