>>725388882
The pre-fall eldar treated humanity sort of like how fallen empires in Stellaris treat the younger civilizations, essentially by being dismissive and uncaring of the goings on of the lesser races.
You gotta understand tha by the point when humanity reached the stars, the Eldar had been ruling the galaxy for like 60 million years because the Eldar have been around as a species from the time when Dinosaurs still roamed the earth.
They are described as having been the undisputed masters of the galaxy at that time but what the nature of their empire was, is left vague. All we really know is that their empire's heart is where the eye of terror is in the contemporary 40k, that they had mastered webway travel, and that their methods of terraforming were slow and took millions of years, they essentially seeded planets with microbes and what not that would over untold millenia, turn those worlds into paradises for the Eldar. At that time the Eldar were essentially immortal, because even when they died of old age (which still took tens of thousands of years) they would just reincarnate trough the protection of their gods which were still alive before Slaanesh was born.
The eldar mastery over the galaxy and the webway was so great that they were able to trap entire stars within the webway, Commoragh is "illuminated" by such captured stars.

The Craftworlders and the Dark Eldar are pale shadows of what the pre-fall eldar were at their height. People who compare them to Golden Age of humanity do not understand what the pre-fall eldar were like in terms of their power scale. Their only comparable rivals are still the necrons and the pre-fall eldar soundly routed the necrons to a point where they had to slumber for 60 million years and wait for the pre-fall eldar to collapse.