D3 seems linear, as you follow a set path.
Where are is the open world, or semi-open world at?
It has always been this way, you just didn't know the path (it almost always split in two or three). Some of the levels are linear, others are more open.
I understand the dungeons may not feel random, but at least they don't have the "underground office park" feel of D2's dungeons. I think the random pieces (from what I've seen) are bigger so it probably feels like it is less random.