DT12 is not that diverse an album imo, regardless of what genre it's labeled as.
Agreed, although the album has grown on me recently. What I liked about ADTOE is that there are songs of varying lengths and styles - you have a few short ballads (FAI, BTS), some punchier songs (BMUBMD, LNF) and epics that are proggy yet not overlong (BAI, Outcry). On DT12 it feels like they tried to stick a bit of everything (metal, prog, ballady moments) into each song and keep them at a similar length, and that makes the album feel a tad samey.
ADTOE is definitely the most varied of the RR era albums imo, and that's one thing I really like about that album. Each song has a clear approach that makes each song stand out.