That is actually a very serious error.
The Ressurection was not necessary for salvation; it is, however, a confirmation of our Faith in Christ and the general ressurection that the faithful of Israel always believed in (alluded to, e.g., by Abraham’s sacrifice of his son, Isaac; the Church Fathers also teach that the Day of Wrath/Judgement Day was alluded to in (then) Abram’s vision:
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And when the sun was setting, a deep sleep fell upon Abram, and a great and darksome horror seized upon him. He may also here have seen Our Lord’s Passion and death upon the Cross.)
Our Lord’s Passion and death are, however, a unity: from the Last Supper until He gave up the Ghost, there is a strict unity, made manifest by the Last Supper’s pointing, as it were, to His death on the Cross. The whole ritual was not completed until He consummated it upon the Cross: it would be a serious error to divorce the sacrifice of the Cross from the Last Supper.
The Ressurection is Our Lord’s greatest miracle and another demonstration of His Divinity: He raised Himself by His own power: no mere man has such a power; it was not, however, necessary
for our redemption or salvation.
Finally, the Ressurection was necessary
as a fulfillment of prophecy, but not for our redemption or salvation: hence it is seen as a miraculous confirmation of our Faith in Christ.