I’ve always assumed the core of D&D was always about slaying monsters. It’s a big part of the game, especially in the newest editions. Combat is heavily prevalent in 3.5/Pathfinder, with a majority of the class abilities, spells, and feats focused towards slaying things. It’s even more prevalent in 4e, whose tactical teamwork dynamic eschewed non-combat mechanics and focused on pushing miniatures around to create Advantage (and put monsters in bad places so that the next acting player gets Advantage).
Looking back at the earliest editions of the game (namely Basic/eXpert), combat is certainly a prime factor. It was born out of fantasy wargaming, which is almost entirely combat-based. (The parts that aren’t are usually things like morale, logistics, resupply, etc., addenda which further combat.) It has stacks of weapons, armor, modifiers for how these interact with each other, hit points to abstract health.
But there’s an element of the game that almost pushes combat as a last resort at low levels. Characters are too vulnerable to last long, enemies having higher hit dice (monsters had d8 hit dice at a time where the strong characters have 4-8) and arrive in large groups. Parlay is a way out, as characters can “overcome” monsters through diplomacy or scare tactics (spells, tactics, outnumbering them, etc.). Experience gained from killing dangerous monsters is marginal, while characters gain huge chunks of XP based on the loot they escape the dungeon with.
And it does fit with Gygax’s source material, particularly the highly influential Conan, Lankhmar, and Cugel the Clever stories. Conan didn’t back down from a fight and was no slouch in combat, but in several stories showed he could use stealth or cunning to his advantage. Fafhrd and the Mouser were also impressive swordsmen, but thought outside the box, bluffed, cheated, and lied their way to victory. Cugel was much the same way, trying to talk his way around something before stabbing you in the chest. All of them had a tendency to get into dangerous situations (namely ruins or lairs) inhabited by dangerous monsters or well-armed bands of outlaws, on the hunt for some piece of prized relic from an earlier, now lost, civilization.
Seeing D&D from that perspective—that the characters are thieves, tomb robbers and plunderers who can fight but, being in a very hostile environment, are better off not drawing too much attention to themselves—gives it a whole different purpose, and gives me ideas on why some of those dopey old mechanics exist. (The “XP from loot” was one of those rules that never made much sense to me; I always thought it was held onto by grognard nostalgia.) It’s not too hard to see a world where characters scrape by in hostile environments, picking through the refuse of older generations, escaping with silver candlesticks and jars of jam. And it makes more sense to me than the player-slayer reputation many OSR-type games garnish, less an exercise in futility and death and more an abstract challenge, a puzzle, a heist. Part of that was because the combat rules lacked balance, but I like thinking outside the box here, thinking up a campaign or game where the theft is more emphasized than the kill.
I’ve been tempted to run a D&D-flavored Fate game, and the world-construct of this viewpoint is one I’d like to explore. Picture a points of light setting. It lacks geopolitical powers larger than collective city-states (save for religion), but is saturated with ruins and crypts full of valuables. There’s no over-arching metaplot threat ala an Adventure Path and its save-the-world goal, instead having more of a gritty, low-fantasy, local/regional focus. There’s still countless threats, from all the humanoid monsters lurking about, and priceless, unknown valuables from a bygone age waiting to be claimed. It’s a cross between Roadside Picnic and Vance’s Dying Earth, done in swords-and-sorcery trappings. An ultimate dark age, where people pay good money for these hard-to-find artifacts, having lost the knowledge of how to craft them.
“D&D as a quest for loot” is a perspective we can only apply to OSR gaming; it’s not a viewpoint we can apply post-AD&D, as there was a paradigm shift somewhere at the end of 2nd Ed AD&D that carried into future editions. Those are all about fighting. The goal was no longer loot, it was saving the planet or eradicating some ancient evil threatening the countryside—extensive metaplots that “tomb robbing” just doesn’t sustain. Those old Gygaxian tomb robbing adventures offered more limited narratives due to their lack of depth and scale, and are a lot closer to a board game mindset compared to modern RPG design. Yet. In a way, we’re coming full circle with 5e/Next and its focus on exploration over both combat and roleplaying, though it blends all three of them in a better balance than most past editions.