Hit points impede improvisation like knocking a guard unconscious from behind.
The action economy forces actions undertaken in combat to be funnelled through an artificial structure (and just as one example, one sees this in threads about "shifting hands" from item to item, and other parts of the "object interaction" rules).
Rules for class abilities, feats etc put limits around improvisation, because they establish minimum degrees of character-build investment to do certain things (like eg inspiring one's soldiers via a speech) and put hard limits around who can produce what magical effects.
Suppose, for instance, my fighter wants to utter a death curse; or my magic-user wants to push harder (Dr Strange-style) to produce a fiercer blast of magical energy? I don't think 5e makes improvising this particularly easy at all.
What does it mean, in the fiction, to have been "hit" (qv damage on a miss)? What does it mean to take 6 hp of damage? What has changed in the fiction?
This discussion is as old as hit points as a mechanic. There's a reason that the simulationist reactions against D&D of the late 70s and early 80s (C&S, RQ, RM) used hit locations and damage to specific locations!
And so what? What would happen? Vincent Baker has
expressly written about this:
Apocalypse World is designed in concentric layers, like an onion.
- The innermost core is the structured conversation: you say what your characters do. The MC, following their agenda and principles, says what happens, and asks you what your characters do next.
- The next layer out builds on the conversation by adding core systems: stats, dice, basic moves, harm, improvement, MC moves, maybe some setting elements like the world’s psychic maelstrom.
- The next layer elaborates on the core systems by adding playbooks, with all their character moves, gear, and additional systems; and threats, with their types, impulses, moves, fronts, and maps.
- The outermost layer is even optional: it’s for your custom moves, your non-core playbooks, your MC experiments, stuff that doesn’t even appear in the book.
A crucial feature of Apocalypse World’s design is that these layers are designed to collapse gracefully inward:
- Forget the peripheral harm moves? That’s cool. You’re missing out, but the rules for harm have got you covered.
- Forget the rules for harm? that’s cool. You’re missing out, but the basic moves have got you covered. Just describe the splattering blood and let the moves handle the rest.
- Forget the basic moves? That’s cool. You’re missing out, but just remember that 10+ = hooray, 7-9 = mixed, and 6- = something worse happens.
- Don’t even feel like rolling the dice? Fair enough. You’re missing out, but the conversational structure still works.
Or:
- Don’t want to make custom moves and countdowns for your threats all the time? That’s cool. You’re missing out, but the threat types, impulses, and threat moves have got you covered.
- Don’t want to even write up your fronts and threats? That’s cool. You’re missing out, but your MC moves have got you covered.
- Forget your MC moves? That’s cool. You’re missing out, but as long as you remember your agenda and most of your principles and what to always say, you’ll be okay.
The whole game is built so that if you mess up a rule in play, you mostly just naturally fall back on the level below it, and you’re missing out a little but it works fine.
The idea that that system doesn't support improvisation baffles me!