Not really. The Ancient Aliens build civilization predated Kirby and was not part of Marvel but Kirby used it to launch his own ideas. For example he copyrighted a 4 page tv script which was all about Judgement by the Gods, and it was in part a WW2 metaphor. Stuff with Judgement, Armageddon, The Holocaust, What We Owe Each Other, Mass Media, etc.
Then Kirby was re hired back to Marvel and was promised he got to do freedom to do his own thing. And he did so for the first half of the 19 issues Eternals. The goal was not to connect The Celestials, The Deviants, The Eternals, Humans, to mainline 616 Marvel. But Marvel said midway through Vol 1 your sales are not good enough so you better start doing crossovers with our IP. Thus we get Robot Hulk, and the Eternals Vol 1 was canceled after 19 issues.
So Kirby Eternals with those 19 issues are not like The Chariots of the Gods book (which is not Marvel but launched the Ancient Aliens craze with all its creepy stuff I will not talk about due to board rules ), and likewise almost all of The Eternals and Celestials lore came after Kirby in the 1980s and was established by different authors in non eternal books such as What If? Issues 23 to 30. It was those issues that connected The Eternals to all these Earlier Concepts including some of the Stan Lee alien races that are part of the Sol Solar System which includes Earth.
Originally Posted by Wikipedia the Eternals