Yeah. A world where Gods can influence directly and wizards can tell physics to sit down and shut up is not always going to be realistic. Though Tolkien did say that the more fantastic the "unrealistic" elements the more grounded the realistic elements need to be.

But DnD is a game. Fun is the purpose. As such some things are fudged away from reality to make it more enjoyable. Realistically every time you got hit in DnD you should suffer status effects ranging from blood loss dizziness to lowered mobility. But that makes it unwieldy and less easy to play, so it gets fidged in a HP mechanic. Such is life.

Realistically a dagger to the throat is instant death. In DnD it ends up being maybe 6 damage. Burning damage should mean rolling will to resist pain from every action. It becomes a bit of damage each turn and that is it.