What I find is really useful is then to tie this back into character creation. If your campaign is about the conflict between the gods of Order and the primordial forces of Chaos, then this should echo in the characters that are played in these games. Backgrounds, classes, feats, whatever, any character made in such a campaign should bear the mark of that campaign. If you make Joe the Fighter in that campaign, then Joe should have some distinctive element that ties him into this conflict between divine order and elemental chaos.
I always feel like every campaign should start with a premise of who the PCs are, in a joint discussion between the players and DM.
I've played in campaigns where the DM shares a lot of information and the players come into the game with characters designed to fit into the game where that the DM wants to run. And, I've also played in games where the DM shares nothing about his plans and every player creates their character in a vacuum, producing a party who have no reason to work together or to pursue the DM's plot hooks. I think the first type of game is a lot more fun.
I commented on the same curious lack of connection to 5e.While campaign themes are a fine topic for discussion, I have no idea whatsoever what that article has to do with 5e's design. Nor is there even a nod to that discussion in the article.
Don't get me wrong- it's a fine article (for being, essentially, a list of a few themes). But I thought that WM was supposed to be about the work on 5e, so I found it disappointing.
You know what I'd like to see in a Wandering Monsters article? A discussion of the corrected monster math. Or, if it's in the cards, an article about the rehabilitation of some loser monster or other (tirapheg, umpleby, tojanida, phantom fungus) into something with a chance of seeing some use. Or, really, anything about 5e's monsters.
EDIT: Also, I find the idea that "exploring a world" is a theme on the same level as "there's an Elder God and a cult and..." to be kinda silly. Classic 1e-style sandboxes tend to NOT have a single theme, instead moving from one to another as the group moves from one adventure to another.