I've got two Moldvay/Cook/Labyrinth Lord games running right now. In one, the group has just returned from a dungeon, sold their loot, and is considering what challenge to tackle next. Nothing unusual there.
In the other, in spite of being in an efreet city on the Plane of Fire, the last game was largely taken up by the blossoming romance of the single PC and an NPC. Some clues were gathered, some mysteries were solved (which, of course, led directly into new mysteries needing to be explored), but mostly it was conversation about the difficulties inherent in a relationship between a dwarf who'd been transformed into a nixie and a human cleric. I don't think we rolled a single die the entire game.
Are we still playing D&D? Yep. The nixie could give her beau the ability to breath underwater, the cleric prayed for his spells in the morning, and their efreeti host had 10 hit dice and the ability to create illusions at will. I'd be shocked if nobody else ran games like this. In fact, I know other people do. It might not be typical, but it does happen.
And this is the way it's supposed to work. The point is for your group to take the game and make it their own. Do you want to destroy the great artifact of evil and return the rightful king to his throne? D&D can do that. Do the PCs rarely leave the city-state and instead strive to make their guild of Blades and Shadows the masters of every criminal enterprise within its borders? D&D can do that, too. Maybe the PCs are all students in an ancient and storied thaumaturgical university, or mamluks of the cabal of brain-eating tentacle-monsters who rule the world.
This is why the modules of original D&D were so bare in terms of setting and story. They were built to be dropped into any of these campaigns. Sure, the assumption was that you'd have to march a few days through the wilderness to reach the The Slave Pits of the Undercity, but they could just as easily be placed in the sewers of your campaign's largest metropolis. You were supposed to take what TSR and others had made and make it your own. The modules of those days way back when were not so much games or stories, but miniature sandboxes. Some might not fit as well in your campaign as others (funhouse dungeons, for instance, are a poor fit for my campaigns), but the bulk of the translation work was up to the DM and players.
This is why I tend to be pretty vague when writing about RPGs and campaign construction. What's perfect for my game might not have any place in yours. I tend to run relationship-centric campaigns, were groups A and B team up to combat the forces of the loose and fractious alliance of C, D, and E. Other campaigns are focused on a particular location (Ptolus or the megadungeon campaign). Some are like action movies, with the barest plot stringing together action scenes like beads on a cord, or grand strategic visions where logistics and planning take center stage. The important thing, of course, is finding what works for your group and what doesn't. Learning what you don't like can be as important as figuring out what works.
Image credits: John William Godward and Paul-Marie Lenoir.