Which, really, it was. I've heard a lot of bands whose debut albums sounded very different from the rest of their work. And even if a few of the core elements for those bands were the same, there were still quite a few other integral elements that made them sound very different and Dream Theater are no exception. And the thing is, yes, often certain things that made the band popular, or just things that people love about the band are missing from the first album. It's understandable for many reasons.
Another thing about WDADU, the actual songwriting, the music, DT hadn't found their sound yet. They were on the right track, and Ytse Jam, I think is the closest they got. But honestly, most of the songs on the album, great as they sounded, had a very strong Fates Warning vibe to them, and MP has admitted that in the liner notes of Awaken The Guardian 2005 edition. But if you listen to Images and Words, and the rest of their stuff from there on out, I honestly can't think of a single song about which I can say, "Yeah, this sounds like Fates Warning".