The focus on "stuff that the PCs can poke, prod, and inspect" seems to me a natural for 4e, with the amount of time typically spent in an encounter (especially a combat encounter).
Module B1 goes further than usual in the description department, but there is a shortage of dynamic situations before the DM populates the place. There's a lot of "scenery", not so much in the way of interactive gadgetry. It can be especially disappointing when players spent time getting, say, a locked (and possibly trapped) door or drawer or chest open -- to find it simply and dully empty.
There are rooms that really stand out, indeed are of iconic status, such as the pools. There are some lively features, such as a certain cat. In the end, though, too much is -- considered in abandoned isolation -- just enigmatic rather than engagingly mysterious.
The missing ingredient, of course, is monsters. I think one might profitably regard those also from more of an "Original D&D" perspective at first. Multiplication of combat stats and rules can add a bit of interest, but I see less really exciting variety there than in tactical and strategic considerations.
I mean the considerations that come into play when one considers a creature as a creature. What are its interests, and how will it pursue them? What is its place in the environment, and how does it interact with the other critters and/or beings there?
If it comes down to a fight, then the interaction of monsters and environment can help turn another standard-issue slogging match into an exciting situation.