The Passover is part of the Old Law. The commemoration of the Last Supper enshrined in the Eucharist, which is the Body and Blood of Jesus, is the New Law.
We no longer wait for the Messiah. He has come, and He has delivered His people from their sins.
He has risen, and is among us. That is Easter, and that is why we celebrate this great feast.
"Christ, our Passover, is sacrificed for us. Therefore, let us keep the feast." Yep, sounds pretty familiar.
Isn't it interesting how many times God punished the people for polluting their religion with pagan forms of worship stuff?
I could go on for pages with sources confirming the pagan origins of the kirchs Ishtar celebration .It is well documented and a proven FACT. I would suggest you read The Two Babylons by Alexander Hislop, Come OUT of Her My People by Dr.C.J. Koster, or get Lew Whites fantastic book Fossilized Customs to learn more and to be informed!
Knowledge can be fun! shalom