I don't think the setting issue has anything to do with it.
And I can't think of anyone else who doesn't like 4E that has even ever mentioned this as an issue.
Usually, you move to a new edition for fear of the prior edition being marooned and no longer supported.
Near as I can discern, the prior edition of the game is currently better supported than its sequel.
That's a distinction with a difference.
I think people are looking for rational business explanations where none exist. If 4e is not as popular as it could have been (and, really, who is to say how popular it could have been?), I wager it's because they changed some stuff, some people didn't like those changes, and pretty soon it became sort of internet cool for those "in the know" to bash WotC. It's easy to hate on the big guy, but then again, it merely serves as continued evidence that the big guy is in fact still the big guy.![]()
I would argue that part of the success of Pathfinder is its support of Golarion. I have no idea how many copies the Chronicles books sell, and they are probably much less than, say, the Advanced Player's Guide or the Bestiary I or II. But it isn't about raw sales, it is about bringing the game world alive and keeping it alive. I also think that Paizo has proven the old adage wrong, that producing setting material and adventures is not profitable. They have struck gold with their subscription model and backed it up with quality products, and quality - if it is marketed well - always does well.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.