I'm curious about this too. On the engineering side, tools like Solidworks and Fusion start from extruding a planar sketch— which is a model that maps well to conventional manufacturing techniques, but isn't very artistic.
Of note, there is an interesting parallel between this sketch/extrude/cut approach that Solidworks uses, and the Brush approach you used to use to make Half-Life and Source engine maps. (I don't know what the current tools, e.g. for Unreal use).
