Yes Easter, Christmas, and "Sun"day observance are of pagan origin that pre-dates Christianity, "The Truth"
Once again, and it's not going to change
Jesus gave the church a direct instruction on how to "Remember Him" not his "Birth" or "Resurrection" but his "Death"
1 Corinthians 11:23-26KJV
23 For I have received of the Lord that which also I delivered unto you, that the Lord Jesus the same night in which he was betrayed took bread:
24 And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me.
25 After the same manner also he took the cup, when he had supped, saying, this cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me.
26 For as often as ye eat this bread, and drink this cup, ye do shew the Lord's death till he come.