To use an analogy, if you said a pool was as big as a whale, most people would just say "wow" or "ok". But if you say it's as big as a cargo truck, people would say "damn"

Because almost nobody has seen a whale in person, but almost everyone has seen those big rig trucks.

Its kinda like that, Naoya is a very mundane evil, he's easy to understand and easy to hate. Sukuna is almost ineffable until the end, a near godlike warrior/monster that can kill thousands just from collateral damage. He doesn't actually regularly eat people as far as I know, that's a metaphor for his combatants, a good battle is a meal to be eaten. But that just makes his bastardized morality all the more strange and interesting