In the ancient Greek religions, were the various myths about the gods just basically fanfic written by different people, or were there certain people whose job it was to write the stories? Was there some body that determined whether the stories were supposed to be canon or non-canon?

by graaahh

And if there was such a group, what kind of criteria did they use to make those decisions?

metsman913

To add on to this question, why did the Romans basically just copy Greek mythology and only change the names?