It comes down to what did Jesus change about the priesthood?
1. he is the eternal high priest and offers sacrifice for sin in Heaven. Thus animal sacrifice has been abolished. *** how can you keep feasts as described in Mount Sinai if they don't have animal sacrifices?
2. He abolished the requirement to be a Levite or even a descendent of Israel to be a part of God's people.
3. All people with the Holy spirit are God's priests and to speak as Oracles of God.
He showed us how to honor Him with Passover, The rest if His Holy Days didn't require us to take the Blood of a Lamb and spread it in the two door posts (our arms and hands, which represent our works) and the Lintel (Which represents our head, or mind) or eat the Flesh.
But even this was instruction was for the people, not the Levite.
Lev. 23:1 And the LORD spake unto Moses, saying,2 Speak unto the children of Israel, and say unto them, Concerning the feasts of the LORD, which ye shall proclaim to be holy convocations, even these are my (The Word which became Flesh) feasts.
That is why there is no mention of these feasts in Jeremiah or Hebrews. They are not part of the Levitical Priesthood Jesus inherited.