I don't think you can make such a sweeping generalization. Look at Radiohead, look at U2, look at Madonna. Time and again those bands have shifted their foot to something very different, essentially reinventing themselves at the expense of losing a lot of their fans.
Problem is IMHO, DT doesn't really have a visionary. There is no Roger Waters, no Steve Wilson in DT. Sure, they all love music and love making music, but none of the DT members seems to have that primal urge to express their world view into music.
A lot of people who I have shown DT to have commented "you know, I have to say it's incredibly well-executed. But, it doesn't do much for me", and over the years I kinda realized there was something to their point. I love(d) DT for the surgical precision, but over the years I've somewhat grown out of the appreciation of mere mechanic excellence, and then you realize that DT doesn't offer too much in artistic vision. I've said this before and gotten shitloads of flak for it, but DT just barely make the label "artists" to me. In my view, they're 98% musicians, and 2% artists.
rumborak