Was the Haggadeh written after God pronouced that His Gloy has left Israel? Ichabod?
If you're asking that to assert that the Haggadeh is not scripture, don't bother. No-one ever claimed it was. But it WAS what Jews were using at the time of Christ. Seems funny neither Jesus, the apostles, or His church ever made mention of the fact if it was true that they had incorporated pagan rituals.
And, by the way, even according to the fallacious Protestant notion of his glory having left Israel for good several hundred years before his glory was born unto Israel, there was a gap of a couple hundred years between leaving Babylon and this de-Glory event.
Come to think of it, have you ever even BEEN to a seder? The notion that the Hagdadeh is a Babylonian thing is just so absurd. It's not like the Easter Bunny where you ask, "Well how did he become a part of this?"