Today Dov Bear reposted (on Facebook) a piece of his from 2007 about the forms of the Seder being taken from the Roman Symposium. This is hardly new and is well known (though evidently not in all circles).
Yet some commenters objected, on the grounds that such "borrowing" would mean that "tannaim and amoraaim were stupid and needed the greeks to help them with our holy things".
One of the most beautiful things about Judaism is that our religion is, in a sense, a time capsule. We adopted so many things from so many vanished cultures and made them our own. Half of what we do came from other cultures.
The Italian Carnival, which started in medieval times but mostly (though not completely) petered out by the end of the 18th century? Where do you think we got the custom of dressing up on Purim?
Dreidel? Based on the Teetotum, a Eurpoean gambling top many hundreds of years old. Even the letters we use, supposedly standing for Nes Gadol Haya Sham, were really gambling codes.
Chassidishe Levush? I don't think anyone, even Chassidim, doubt that it came from Polish and Russian nobility.
Let's go back further. The names of our months? (Nisan, Iyar..) We got those from Babylonian culture. Those names are never mentioned in the Torah.
And yes, the Seder is mostly borrowed from the Symposium. So what? The beauty is that Judaism throughout the ages has taken things from Chol to Kodesh.