I
actually like HP. If there's one sub-system detail in D&D that really captures a bit of fantasy genre, it's Hit Points. No, really. Hear me out.
I've played a lot of games, and I do find I like D&D-style hit points better than most alternatives. Sure, they're vague, dissociated, and completely unrealistic. Sometimes they even paint the game into self-contradictory-seaming corner. But, they're simple math, they require no extensive checks or tracking of individual injuries or severity, and perhaps best of all, come with no
Death Spiral. That is, when you lose hp, you don't lose ability. You keep fighting on, heroically, at full strength to your last hp, if need be. And, that needn't be - you can seek help, run away, or switch tactics when you realize
from your declining hp total that you're overmatched. That's actually something that happens in genre, heroes will be kicking ass with great efficiency, yet, tho none are visibly wounded, one of them will shout "there's too many of them" and they'll retreat, or pull out a new trick or whatever. How do they make that judgement, you're all fine, you're not obviously losing? They're low on mysterious ill-defined hp.

Nor is that the only genre-faithful perk of the hp mechanic - there's also the Heroic Come-back. When the heroes get trounced by the obviously-too-powerful villain, only to find the courage rally and carry the day. OK, in D&D it also involves the Cleric casting a spell or something, but still you get that come-from-behind cadence that battles in genre (and action movies) so often have.