I think the major contributer to the problem is the huge-sweeping-multi-book-single-story-epic just isn't a viable form. And I think a major contributer to that problem is, the writers who are inclined to pursue that form don't know when to stop. (Terry Brooks would call this a failure to outline, meaning if you don't know where you're going when you start, you'll just go on and on.)
Is anyone else hoping Rothfuss's 3rd book is the last one?
I'm not sure if the writers engaged in sweeping epics are megalomaniacs, or if it's a problem perpetuated by publishers wanting to indenture writers, or if stand-alone books don't sell as well, or if writers don't want to do them as much. But I'm really starting to not want to see any more series. At all. It's to the point where I cringe whenever I see something new and see it's "book 1 of who the hell knows." There's a reason Netflix originals are released whole seasons at once. They understand that's how people want to consume entertainment. Serialized entertainment is becoming obsolete.
More stand-alones, please. There's something to be said for being able to tell a *whole* story in just one book. (That something is *thank you!*)