I think you've missed a vital reading of Scripture (or have been led astray about Passover being "nailed to the cross").
Luke 22:15-16 (NKJ) -- Then He [Jesus] said to them, "With fervent desire I have desired to eat this Passover with you before I suffer; for I say to you, I will no longer eat of it UNTIL IT IS FULFILLED IN THE KINGDOM OF GOD."
Where do you get the idea that the Passover is fulfilled? Certainly not the Bible! Jesus plainly said it won't be fulfilled until the Kingdom of God. And the Kingdom of God will not come until Christ returns.
Also, Paul says:
1 Corinthians 5:7 (NKJ) -- Therefore purge out the old leaven, that you may be a new lump, since you truly are unleavened. For indeed Christ, our Passover, was sacrificed for us.
How can Jesus Christ be OUR Passover if we don't OBSERVE Passover???
The Bible makes plain that Christians are to continue to keep God's Holy Days, most especially his most precious pearl, the Passover.
The OT Passover was indeed a foreshadowing of the sacrifice of Jesus Christ, the Lamb of God. And there is much corresponding symbolism. But just as the Exodus from Egypt was a done deal when the Children of Israel left, yet they were commanded to continue to observe the Passover forever (Exodus 12:24); so too the memorial of Jesus' sacrifice (the Passover) is to continue to be observed by the Children of God.
Israel was told by God to remember his wonderful works. And a key to that memory is his appointed Holy Days and Feasts. Christians too need those memory aides. And Passover is chief among them. And Jesus told us to remember him:
Luke 22:19 -- And He took bread, gave thanks and broke it, and gave it to them, saying, "This is My body which is given for you; do this in remembrance of Me."
Paul adds his support for this as well:
1 Corinthians 5:7-8 (NKJ) -- Therefore purge out the old leaven, that you may be a new lump, since you truly are unleavened. For indeed Christ, our Passover, was sacrificed for us. Therefore LET US KEEP THE FEAST, not with old leaven, nor with the leaven of malice and wickedness, but with the unleavened bread of sincerity and truth.
God's Word, The Bible.