> Graphically more primitive than Doom in most ways

They didn't use a raycasting engine, though - the maps were full 3D (and so were some of the environment pieces - benches and the ankhs come to mind). Because of hardware limitations, your viewport was limited to about 1/4 of the screen...

In a lot of ways, they were technologically superior to the Doom engine - except they were slow. The same engine ended up being reused for System Shock (and 2, if I remember correctly).