I’d take Genesis 6 and The Book of Enoch over any “Urantia” type books any time. They provide also a very good explanation about the “superior” genetics.
The archaeologists assume that the same people who operated the site also buried it.
Not necessarily. It may be that (as frequently occurred among ancient peoples) the site was a place of idolatry, human sacrifice and so forth and another group, led perhaps by a man such as Enoch, came and chased the wicked people away and buried the site. Later on, the site sprang up again for similar use.