Jesus went to the synagogue BEFORE his Passion, Death and RESURRECTION, and THAT is the key to right understanding.
Up to the point of Christ’s Passion, Death and Resurrection was pursuing His Heart’s desire for the “Salvation of the Jews” [read: Mt 10:1-8]. …AFTER the Passion and His crucifixion by the Jew s[ or all of humanity]; there was still a great effort at converting the Jews, the MIssion was expanded to "the entire world " Mt 28:19-20.
Also what Jesus came to accomplish was not to update Judaism ; BUT rather to introduce an ENTIRELY NEW RELIGION; one respecing past Traditions, while a the same time making sure there were sufficient differences so as to insure that what He was doing WAS new. … In effect Jesus intends to REPLACE Ot JUdaism with Catholicism: I AM THE WAY, THE TRUTH & THE LIFE
So the Early Church choose to celebrate; SUNday the Day that Jesus rose from the Dead; precisely and theologically because it Is Easter Sunday, not Christmas, not Good Friday that is the 1st cause for Christian Celebration not that the others are not essential.
It is BECAUSE of Christ Resurrection that Jesus became MAN, like us in every way but sin. It is because of his resurrection that all of humanity for all time is now REDEEMED.
The terms Redemption & Salvation are NOT synonymous.
Redemption MEANS that because Christ ROSE from the DEAD, then we ALL NOW could and WOULD have the opportunity to FOLLOW Jesus into heaven which had been on “Lock Out” as a result of Original sin. Once again the GATE to heaven, to which He entrusted the KEYS to Peter and the RCC was a possibility.
Salvation: Means to speak to that “possibility” of salvation; that is Highly conditional, a life-long process of proving time and time again [Isa 43: 7 & 21] our love and humility through knowing and then DOING all that Christ actually ask. It is FAR more than just acknowledging Christ as our Personal Savior; though that is the essential FIRST step.
SUNDAY celebrates Christ’s Resurrection AND the worlds Redemption. And the Power and Authority of ALL the Keys to heavens GAte permits the RCC to do this,