They never interfered but the sight of them probably inspired some of the myths and world religions that exists today.
At the same time, it's contradictory because while you have Thena and Sersi who may have inspired the mythical Athena and Circe, characters like Thor exists in the MCU and Thor 4 is going to introduce Russel Crow as Zeus. In the comics, the mythical Gilgamesh also exists and teamed up with Hercules. IMO, it undercuts any real influence the Eternals may have had in shaping human history. It just shows how the characters were originally never meant to be part of the MU which might be why the movie is opting for a style that's different from Thor and the Guardians.