It's strange you think the "history covered" was essentially meaningless.
Did anyone even pick up that Namor's people were born within five years of the Tenochtitlan event in Eternals and they were both located in he Yucatan? And than when the Talokan attack or move together, they do it in an avian structure (a triangle or pyramid) like the Eternals appeared to ancient man in the opening scene?
Is it connected?
Also, basically to quote myself from the site created to explain Eternals, the passing of time in the film is not simply "laying of foundation". What happens over a long period of time? Evoluton. Eternals are beings who span great periods of time, thus, the director can show us things like the character Kro (mostly ignored) who I believe may have been a mutant. How else do we explain its ability to take the powers of an Eternal Rogue-style? And, with taking that power, to evolve suddenly.
Kro sped up evolution immensely. After absorbing Ajak, it's "paw" and spine changed instantly allowing it to stand further upright. Upon absorbing Gilgamesh, it stood completely, developed a full hand and could speak and interpret Ajak and Gil's memories.
We saw a mutant in the MCU - a rapidly-developed one - for the first time and fans blew Kro off as some fake and trick character hiding the Celestials as the villain.
How short-sighted.