I agree with most of the rest of your post, but not this bit. D&D is highly focused. It’s a combat simulator with a few vestigial bits of a dungeon crawler resource management game and some tacked on elements to make it appear more rounded and less focused. But it’s still a highly-focused combat sim at its core.
See, that's a common perception that I don't agree with, because D&D is sui generis. To go back to the book that I often reference (and you are familiar with) ... D&D wasn't a ruleset to begin with, so much as it was a toolkit to make TTRPGs.
And that DNA has continued within the game.
Was D&D a combat simulator? Kinda, but not a very good one.
Was it just a "golden hole" dungeon explorer? Sure, but not really.
Was it an excuse to get yer freaky roleplaying on? Yes, but also not just that.
And so on. D&D is both a desert topping, and a floor wax! That's really what gets at the heart of so many debates ... there are a lot of people who hate D&D because of that lack of focus. And there are others that love that same aspect. And really, it's the exact same thing that these people love/hate - that lack of prescriptive demands as to what you play.
If you're one of those people that prefer crisper modern rules, you might go on about how there are these combat rules, and undefined social rules. And while that is completely correct, that also misses the point of why other people like it.
As I said- it's hard to generalize examples from this game which has a history and player base that's different than that of almost every game around.