As it should be.
I practically wrote a freaking essay about this shit 25 pages ago.
The short answer is that there were writers who did want to connect the real world and SW's world but their stories rightfully got canned (although the second story would've been fine in itself if they just removed the real world connection and a few answered questions that didn't need to be answered). So the official (pre-Disney shit) explanation is that humans came from either Coruscant or Tatooine.
As for the "long time ago" narration, it was supposedly part of an early idea from ANH's conception period where the opening was originally going to be told from the perspective of the droids in the future.
Years later this idea would be adapted in the early 2000s via a comic that was released in Dark Horse's SW Tales series which contained canon, non-canon and ambiguously canon stories. One story in particular fell under "ambiguous" that takes place an unknown number of centuries in the future, maybe even more/uncountable. In this story that takes place on a primitive world, we see a duo of enslaved alien children wandering away from their ruined village and hide out in cave where they seek out "The Storyteller" who is none other than the decaying and broken remains of C-3PO...
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C-3PO has lot pretty much everything, including his sight. His only possession is Luke's lightsaber. The local village referred to him as "The Storyteller", an ancient relic who would share with you "stories" and "fairy tales" from a long time ago in a galaxy far far away.
Upon telling the children the tale of his friends and many adventures, they are skeptical but inspired nonetheless, but it would be the last story 3PO would ever tell as they were then found by the overlords of the slave children. The older child warned his brother to flee while he tried to hold back the aliens, but his efforts were for naught, as they proceeded to destroy the droid and kill the older alien child trying to protect his brother and 3PO.
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The surviving child would then use 3PO's story and Luke's saber to give him the courage he needed to fight for freedom.