So what? Many cultures believe in tree spirits; women are inferior, autocratic rulers, magic, love potions, an afterlife, etc. You are just cherry picking stuff to fit your conclusions.
warpus said it was suspicious we have only 1 person for the story, so it matters if the rest of the world believed in a golden age of gods, demigods and heroes. Advanced civilizations meeting their demise in a natural disaster is not unique to Atlantis.
Your guys had gene editing and space ships and couldn't find gold except on earth and then needed salves to mine it. I kind wonder about their energy source when their planet was way the hell away from the sun and they didn't freeze to death. How would humans on an earth-like planet survive on an orbit that that took them 1800 years away from the sun? How long has Voyager been going? 44 years and it is now 14 billion miles away. Hmmm... 1800 years would put your space aliens quite a distance for most of their orbit. And in the last 400,000 years the only gold they could find was on earth? Do we know how gold dust saves their atmosphere? Any chemistry involved?
I dont know how life would/could evolve on a planet with such a highly elliptical orbit, but according to Sitchin Nibiru is a larger planet, internal heat could drive life - life it may have already had, life it brought to Earth. Life could predate our solar system, it could have survived the death of another and arrived here 4 bya. I consider the description of Nibiru and its need for gold the weakest part of his theory, I cant imagine humanoid life on such a planet even if life on Earth has a shared origin. But he's getting that from their writings.
According to the Mesopotamian texts these people from the sky were mining the gold themselves but grew weary and sought another way after 40 Sars/144,000 years (1 Sar/divine year is 3600 Earth years) - Enki found a creature roaming his southern domain and they modified it to take over some of the labor. The Zulu believe their ancient ancestors - 'the artificial ones' according to the myth - waged war on the apemen when a special celestial object rose in the sky.
Sitchin solved the biblical mystery of God's assertion in Genesis 6 man's days were numbered 120 years, although I cant imagine he was the first:
Now when men began to multiply on the face of the earth and daughters were born to them, the sons of God saw that the daughters of men were beautiful, and they took as wives whomever they chose. So the LORD said, “My Spirit will not contend with man forever, for he is mortal; his days shall be 120 years.”The Nephilim were on the earth in those days—and afterward as well—when the sons of God had relations with the daughters of men. And they bore them children who became the mighty men of old, men of renown.
According to Berossus 10 preflood kings ruled 120 Sars - 432,000 years. These reigns were in multiples of 3600 years, changes in kingship were accompanied by the arrival of Nibiru in the vicinity. Sitchin said mans days were numbered 120 years because that was the time between the arrival of the gods and the flood.
So it was 40 Sars (40 x 3600 = 144,000 Earth years) after they arrived Enki started playing god with our hominid ancestors to produce slave labor - the Adam was taken by God eastward to his Garden to work. Westward of the Garden is Africa. The process of expediting our evolution began 144,000 years after they came to Earth or ~300,000 years ago, but its less clear when our common ancestors lived, Sitchin said the myths describe the first peoples as sterile or unable to procreate.
That ability was eventually given by Enki, the serpent deity, and appears in the biblical Garden of Eden as the 'curse' on Eve - for listening to the Serpent you shall suffer increased pain in child birth. Increased pain in child birth is indeed a curse on anatomically modern women, but by telling Eve her future reality the Bible is relating an evolutionary leap from over 200 kya. Actually, evolution permeates the Garden story, Adam and Eve were naked and unashamed, innocent, not knowing of good and evil.
As for why mine the Earth, why not? Even if there was no gold theres plenty of resources, including food and a potential slave labor force. If we trekked to another solar system looking for resources wouldn't we set up shop on the planet harboring life?