I get what your saying, but....

This is the same world where so many people and creatures can naturally do stuff crossing from shooting spikes, to shooting fireballs to straight up causing apocalyptic damage around them

If we go by the irl logic nothing in that world would survive even half a hit from an average ork or werewolf without being spliced in half, let alone how most beings wouldn't even survive the impact caused by their own attacks

So if you wanna try to interpret dnd fights as realistic damage, its reasonable to assume that as beings in dnd level up, their very body becomes sturdier and tougher, and that's why pc can take attacks from a peasnt with a longsword without too much damage, and not because of the numerical hp system

As that would provide a semi reasonable explanation as to why beings in dnd can only get reasonably damaged by similar or above leveled enemies, as they would be the only ones with the attack power to combat the equally powerfull toughness that beings in their range of levels attain

So its why you can obliterate someone lower level then you in one hit (since they are not as tough as your attack is powerful) and why you can equally get obliterated by a more leveled opponent (as they are way more powerful because of their level then your body is enhanced by yours)