That was for a different reason that does not apply today, other than the 14th could be on any day, not always on a Sunday. We actually follow Rome. St John taught Polycarp regarding the 14th. However it was ROME (Anicetus and Victor) that had a problem with it! Polycarp met with Anicetus in 155AD. Most if not ALL the churches in the East (now Orthodox) kept the 14th. Nicea it would seem was a consensus regarding SUNDAY. 1 Corinthians 5:7
Polycrates insisted in his letter to Pope Victor that “we ought to obey God rather than man."
“We observe the exact day (Nisan 14 for Passover), neither adding, nor taking away"
“For in Asia also great lights have fallen asleep, which shall rise again on the day of the Lord’s coming, when he shall come with glory from heaven, and shall seek out all the saints,”
"Among these are
Philip, one of the twelve apostles, who fell asleep in
Hierapolis; and his two aged virgin daughters, and another daughter, who lived in the Holy Spirit and now rests at Ephesus; and, moreover, John, who was both a witness and a teacher, who reclined upon the bosom of the Lord, and, being a priest, wore the sacerdotal plate. He fell asleep at Ephesus. And
Polycarp in Smirna, who was a bishop and martyr; and Thraseas, bishop and martyr from
Eumeneia, who fell asleep in Smyrna. Why need I mention the bishop and martyr
Sagaris who fell asleep in
Laodicea, or the blessed Papirius, or
Melito the Eunuch who lived altogether in the Holy Spirit, and who lies in Sardis, awaiting the episcopate from heaven, when he shall rise from the dead?”
"And I also, Polycrates, the least of you all, do according to the tradition of my relatives, some of whom I have closely followed. For seven of my relatives were bishops; and I am the eighth. And my relatives always observed the day when the people put away the leaven. I, therefore, brethren, who have lived sixty-five years in the Lord, and have met with the brethren throughout the world, and have gone through every Holy Scripture, am not affrighted by terrifying words. For those greater than I have said ‘We ought to obey God rather than man’…I could mention the bishops who were present, whom I summoned at your desire; whose names, should I write them, would constitute a great multitude. And they, beholding my littleness, gave their consent to the letter, knowing that I did not bear my gray hairs in vain, but had always governed my life by the Lord Jesus.”
Bishop Victor ex-communicated Polycrates and all the bishops who supported him. However, he reversed his decision later on after several bishops, including Irenaeus, intervened.