The statement of the Passover being observed forever is always directed to Israel, in the times in which God is dealing with them as a nation – Exodus 12:1-13; 12:23-28. In fact in Exodus 12:43-50 no Gentile was allowed to take the Passover unless he got circumcised.
This is certainly different than the age of Grace that we live in. In Galatians 2:7 Paul preached “the gospel of the uncircumcision” to us Gentiles and therefore speaks against circumcision in Galatians 5:2 and 6:15. He also instructed the Galatians (hence the Body of Christ – the New Creature) not to be observing days and months and times and years – Galatians 4:8-10. Colossians 2:16,17 directly warns against someone spoiling us of the riches of God’s grace and says:
“Let no man therefore judge you in meat, or in drink, or in respect of an holyday,
or of the new moon, or of the sabbath days: Which are a shadow of things to come;
but the body is of Christ.”
Not only does it tell us not to respect holydays, it also tells us why. They belong to Israel and are a shadow of things to come. Not the present day. In the present day God is dealing with the Body of Christ. Hope all that helps.