To be fair though, most of the issues with D&D can be traced practically directly to incoherence in design. As differing goals clash, the game becomes messy. The gamist elements often clash with simulationist ones, for example, and trying to fix that can make things worse when no one is willing to try to understand the underlying goals in the first place.
Perfect example is the caster rules about not wearing armor and no weapons. That was a purely gamist decision. Wizards don't get armor or weapons because they are meant to be artillery analogues. So, easy to kill but incredibly devastating on the battlefield. But, then the Sim crowd came along and tried to create a reality around this concept and we got all sorts of wonkiness like, despite my character being incredibly smart and quite possibly strong enough, I can never learn to use a sword or wear a suit of chainmail. Because it "interferes with casting".
But, that doesn't seem to apply to clerics... because cleric magic and wizard magic are different. Not sure how they're different and they both use identical rules and often are casting the identical spells, but, they're just... different. So, my wizard can't wear leather armor and cast Detect Magic, but, my cleric can. And this is simulation?
That's just one example, but, I'm sure there are loads and loads more. And, let's be honest, there's a segment of the fandom that is actively hostile to anything even remotely approaching narrativist approaches. The whole "entitled player" schtick is 100% grounded in a complete opposition to anything narrativist being added to the game. So, while D&D is mostly gamist with a layer of sim on top, the whole body of narrativist approaches gets 100% blocked from the game.
If mixing was okay, then, we'd actually be allowed to have the odd narrativist rules module. But, the fandom absolutely will not allow that.