It's not metaplot itself I dislike, but the way they clumsily advance the setting because of it. To use Greyhawk as an example, I like Carl Sergent's From the Ashes stuff, but that is in spite of the metaplot, not because of it. I'd somewhat prefer setting remain static, or that individual adventures advance from a universal set point, rather than from the last adventure (see Die, Vecna, Die and the difficulty subsequent products had incorporating that). Of course, they always will advance timelines, as it's the easiest way to sell stuff; so I would implore them to try and do a good job, and not be afraid to ignore things that happen in bad adventures and novels when the line editor has been less than a vigilant hard-ass. Try for things that advance the timeline in a way that aids DMs, as opposed to whoever is writing the setting's novels.
Oh, and Set, I love the Scarred Lands (esp. Hollowfaust), and I'd forgotten there even was a metaplot. Although I remember much of that elf stuff now that you mention it. The Slaracian Legacy wasn't my favorite supplement, but I did think they did a good job of including ways to run a totally world-changing campaign, but didn't imply that some version of this was somehow going to become cannon for SL.