I actually don't see it as a level-based issue at all. I would characterize it as a variation of the OP's suggestion #1, though.
I think most settings have a schtick. It's a desert world or a world overrun by goblins, or whatever. And, that schtick can carry you for a while. But, after a number of sessions, the game is going to need more than that schtick. It's going to have to be a bona fide interesting and intriguing world. And, in this regard, most published settings fall flat.
For example, I was a huge fan of the Birthright setting. It had two things that set it apart from other settings -- you could play rulers (so they embraced the Civilization game right out of the blocks) and there was this whole Highlander-style bloodline thing. But, in addition to that, the setting was a pretty interesting, semi-Arthurian take on things and there were also just interesting elements to it scattered throughout. Without that second part, a Birthright campaign could only last for a little while, essentially till the novelty wore off.
The other thing that I think kills published campaign worlds it too much detail. You want a living, breathing world, but you also want one you can modify to suit your campaign needs and to allow your characters to impact and influence it, which becomes more important as the game wears on. The more the game setting represents a beautiful, elaborate tapestry presented by the game designers, the more likely you are to be playing "NPC Theatre" than an actual RPG.
Those are my issues w/ most campaign worlds, which is why I have only really enjoyed a few (Birthright and Planescape namely), and have generally pillaged others for ideas and quickly gone "off book" in games I've played or run. We mostly tend to use homebrew settings inspired by books (Icelandic Sagas, The Malazan Series, Tolkien) or history/myth (Ancient Greece, First Crusade) anyway.
@High Level Play
I do think that, generally, way too little thought has been put into how the campaign should evolve as levels go up. It's not so much a problem of adversaries -- there are plenty of powerful ones lying around. There is the problem of powerful, open-ended spell effects, which should change the kind of adventures you are involved in, but I also think that could be solved fairly easily by introducing counters to those effects (as an OP noted, usually done by fiat in AD&D, I'm looking at you "Tomb of Horrors"), or just limiting them in small ways. And, I think some of your high-level adventures can surely be MacGuffin-based and so on.
But, high-level characters should eventually fit into the world differently, and they have typically developed reputations. The Leader of Men thing is pretty hard-wired into D&D, hell, I recall "name level." And, while they have thoughtfully provided me w/ dozens of charts concerning how much silver I owe the limner and the clark on my staff (b/c if there's anything D&D knows, it's charts, them and Rifts), they haven't really produced much material about what kind of adventures one can run and play as a Leader of Men. They haven't given me a huge incentive to product said Men, and so on.
This is a particular issue in D&D b/c the average 16th level party is tougher than the average army, which begs the question as to why I would want to bother leading this Men in the first place.