Agree somewhat, especially if Starlin or someone like that is writing him. There are incarnations of Thanos historically that seemed a bit beyond the level of Earth's most mightiest heroes even without the Cosmic Cube, IG or other end-game devices. But there are just as many stories that show him far weaker than that.
That said, there has to be a reason why the Eternals never dealt with Thanos once and for all. Even with a Prime Eternal and other Eternals whose abilities are at the top of the Eternal scale in some categories, Thanos always seems to eclipse them all. I feel like Thanos has to be powerful enough to present a threat to the multiverse and anyone in it. Not just intellectually, but raw, brute, cosmic force. If not, he falls flat and no one would really fear him.