The community hasn't really warmed up to The Dark Mod as I thought it would. I guess everyone's more comfortable with how the original games look and feel, and I can't say I don't understand it. Thief still plays great thanks to its minimal controls and UI (much unlike System Shock 1, which feels horribly outdated) and looks nice thanks to its amazing art direction (just look at some of the screenshots in here
https://twitter.com/thiefbsp), so I don't think people would feel the need to move on to a clone unless it was that much better.