This is an interesting objection and worth unpacking a bit, as it is at the root of many of the misunderstandings about how old edition D&D works as written. It is tempting to look at play BITD and assume that the game was designed to focus on combat. https://twitter.com/glauer42/status/1275401535099371521

I am aware that Gygax ran a lot of dungeons, and that there was a lot of fighting in the games he ran. But you need to read between the lines. Fighting wasn’t the goal in these games, it wasn’t that it was a combat focused system, it was that in the early days of gaming…

... gamers were learning how to navigate the system and fighting is an instinctive reaction to experiencing the unknown. In the same post linked above it is pointed out that they learned to be more cautious, to avoid combat where possible. That’s the takeaway here, not that…

... there was a lot of combat in early games, but that learning to avoid the combat was how they survived. Many people who haven’t done a lot of actual dungeon crawling think that dungeon crawling is about fighting everything and killing it, but that’s a mistake

Dungeon crawling is about resource management, risk management and exploration. Combat is the result of making mistakes, rushing or just bad luck. If you read over old accounts of gaming in this period you read that many PCs die in this system. The game is lethal as designed.

But I also think this is a red herring. Many people play D&D as a “hack and slash” game because that’s easy, and let’s be honest, many gamers like to kill stuff and fight. It’s visceral and exciting to fight monsters and be challenged by them, kids love that stuff.

The game is combat focused because PLAYERS LIKE COMBAT. The GAME DESIGN, however, doesn’t support this. A glance at the rules shows that the vast majority of your XP comes from loot, not monsters, most first level parties with rolled HP wouldn’t survive the first encounter

D&D works as a “combat focused game” because refs soften the game to make it survivable. They pad HP at lower levels or start PCs higher than first level, they use generous point buy systems, they fudge dice rolls to save PCs, they assign treasure and bloat the PCs power…

… They ignore “in lair” %’s and just let PCs collect loot, they ignore “number appearing” of monsters and reduce risk, they ignore rules for friendly fire, they nerf surprise rules, etc, etc. The VAST amount of house ruling that goes on in early edition games…

… is in part because of exactly this issue, that the game doesn’t support fighting and killing everything, and people have to house rule the game to a significant degree to make it work when that’s the play style. It's combat focused as we change rules to make combat workable

Hot take: D&D is combat focused because that’s the way many people want to play it. The reason I push back on this is that people almost always say old school D&D is combat focused by design, but that’s not the case, it’s combat focused because people like to fight stuff.

Another unspoken aspect of this is skill. Playing D&D can involve a lot of combat, but playing it as designed and playing it WELL, learning to survive the system as written, that takes skill. And the most skilled players don’t wade into combat with everything they meet

If you look at accounts of actual play from BITD you see exactly this. Yes, there was a lot of dungeon delving, but the players who survived and thrived ran away and avoided combat as much as they engaged in it. It’s virtually a trope that you can encounter things well…

… outside of your pay scale in any level of the dungeon, and if you fought these things you would just die. It’s the same for the random tables for making dungeons, these key monster difficulty to level, but there are always monsters well beyond that level of power in the lists

So just to reiterate, AD&D as designed (and I would extend this to other old school games) does not reward combat, it rewards exploration, resource management and risk management, and the reason people think it is combat focused is that many play the game that way

But the only reason the game works is that the ref actively works to soften the rules to make it possible to survive when you fight everything. If you apply the RAW then this style of play fails, which should be a clear indicator that the game isn’t combat focused by design

Until someone makes it clear how the RAW supports combat focus, and this would require some work, I see this as a pretty typical case of “design versus implementation”, people need to stop confusing practice and theory, the way the game is played from the way it is designed