The Core Problem With Dream Sequences

Many dislike dreams in fantasy and science fiction. Who, and how many exactly? Shut up. Anyway, in a modern materialistic setting, dreams are comparatively fanciful. In fantasy or science fiction, the stuff in them can simply happen, perhaps in the holodeck or fairy world. If anything, fantasy/scifi dreams often seem mundane, and who wants a mundane interruption in the middle of his thrilling and thought-provoking speculative fiction narrative? Many, but possibly fewer than the many mentioned earlier.