I think that's getting too caught up on the specifics of the numbers and missing the broader point. Suppose we have a 3.5 Fighter, who simply cannot be damaged by low level characters, because he has DR from various sources that is larger than the amount of damage low-level opponents are capable of dealing (or that we're playing some version of the game where a natural 20 isn't an auto-hit and he has an AC of 35 or something). That guy can just walk around killing everybody. And he can do so forever.
But that's just admitting that you are in a Mythic setting, you're just not allowing the PCs to be mythic.actually powerful immortal D&D creatures in the monster manual being on cosmic cleanup duty.
Honestly, I don't find that all too surprising. Of course people will follow their incentives. If there's no social status to be gained, people won't do anything to gain social status.
It goes both ways though. In 40k, you can save the world. You can take a world that is full ofdemonsdaemons andorcsorks and clean it up and install democracy and improve standards of living and reignite the light of science and end the persecution of mutants. And that's a Mythic victory if you do it in a D&D campaign. It's just that you can run a campaign where you do that every day for a hundred years and still not have fixed even half of the worlds in the Imperium. That doesn't lessen those accomplishments, it just means that 40k exists at a scale that breaks people's brains. The Imperium has been decaying for longer than writing has existed in the real world. It will continue decaying for even longer before things come to a head.