Melville's abundant skill has vanished - Why?

Let's be honest - no matter who's reading it and no matter how much you love "Moby-Dick" and stand in awe of Melville's great power and originality, there comes a point in the dark November of your soul when you think - enough, I don't want to know one more single thing about whales, oil, blubber, tackle, barbs, topmasts, gams, and so on forever. You begin to wonder: what's happened to the story here? Ahab, a dynamic and mysterious character, has pretty much faded below deck. Queequeg, introduced so dramatically in New Bedford, is now just a skilled workhorse (interesting how the hardest and most dangerous work goes to the three men of color, and the humiliation cooks to the black cook). Ishmael is just a lens through which we see the story - no longer a character. And what of the mysterious Filipino boatmen that Ahab stowed away? Melville's abundant skill with distinct characterization, so evident in the first hundred pages (the two shipowners, the strange Elijah, et al.) has vanished. Why? Where? Not to say that it's all part of an overall design, but there is a way in which the entire novel mimes the process of a whaling voyage, embarking with such hope and high prospects, followed by long periods of languor and serenity, then sudden bursts of dramatic and dangerous action, and then hours of hard, even tedious work. It's not what we expect of a novel, there is no obvious arc to the story as in popular fiction of movies, but nothing in Moby-Dick is what we would expect. The novel itself is a voyage - and a quest.