To me is very simple.
The 90`s was the best DT musical period, and they extended that to SDOIT (their last completely satisfying work -2.001-).
Every album from that date, was a little bit more dissapointing than the previous, with SC as a clear low point and BC&SL as a bottom, thanks to that "balls" theory of Portnoy.
With ADTOE (a very safe album -it was the purpose-) they recovered a lot of musical seriousness.
And now, I have a huge expectation for DT12, basically for the presence of Mangini in the creative process (adding Richard Chycki and Eren Başbuğ).