Running more and more of 5e, and I'm questioning a lot of the assumptions of D&D. Volo's plays around with how some of the monsters work and their statblocks, so last session involved some monsters that were easy to hit (low AC) with a decent amount of HP and multiple low-damage attacks (making them likely to strike and whittle away at HPs). The monsters had a bonus to some ability scores and a penalty to others, and it suddenly was apparent to me that it didn't really matter.
Does a monster having a +10% chance to succeed on a saving throw actually matter? What about a monster with an Armor Class of 15 vs. 13? Does that design component really add anything to the gameplay experience? In theory, yes; in practice, possibly.
On the players' side of things, mechanical fiddliness matters. In the course of a campaign and many rolls, the mechanical complexity creates a noticeable difference. Mechanical distinctness between characters matters to some players. Likewise, Power escalation is a core principle of D&D, and I think that removing it would be a mistake (the zero-to-hero arc).
Yet there's a part of me that wonders if the game of D&D would be missing anything if it stripped away the majority of this complexity from the DM's side of things. To reframe the question: how much of the "D&D experience" is based on the numerical treadmill? You find a +1 sword so that you can fight a monster with +1 armor. You gain +3 hit points so that you can fight a monster that does +3 damage. And so on.