Agreed. There are two references in scripture about them meeting on the first day of the week. This seems to be the reason for it's continued practice by the early church writers. And in my opinion John in Rev 1 did not mean Sunday when he said he was in the Spirit in the Lords Day but that he was translated by Spirit into the Day of the Lord and all that he recorded had to do with the future Day of the Lord. However, some early church writers a few hundred years later already being used to misinterpreting it as Sunday tried to suggest that Sunday was called the day of the Lord in the first century based on this verse in Rev 1. I do not think they called Sunday the Day of the Lord until much later. Even though we know that the Jews observed sabbaths the gentiles did not observe sabbaths and they were taught by Paul that they did not need to and to resist the Judaizers who attempted to pressure them. This war is still going on.
The book of John was likely written in late AD90.
The Jews had developed hatred toward Jewish Christians early on, but it intensified after the fall of Jerusalem because Jewish Christians left Jerusalem based on divine warning, and escaped death and slavery that the rest of the Jews in Jerusalem experienced.
In AD 90, a section was added to the eighteen benedictions recited in the synagogues which denied the Messiahship of Jesus. As a result, conscientious Christians were not able to fellowship with Jews on Sabbath in synagogue worship. So, there was some intensification of punishment.
You are right in that the eschatological Day of the Lord could have been the reference here, but it could also be the Lord's Day in regards to Sunday. And, Jewish Christians were fellowshipping on Sunday and other days with Gentile Christians, observing communion with them. They may have attended synagogue on Saturday, to hear the Scriptures read, but they also met with a Christian focus on Sunday and other days.
The practice of meeting on Sunday is established by Christian writings as early as AD 135. Even the Seventh Day Adventist church admits that. Their historian, Samuele Bacchiocchi, researched this issue. He expected to find a much later date, perhaps blaming the typical "boogie man" of Sabbathkeepers, Constantine, but in fact, he found references that dated to the early second century.
Constantine only required a rest day for soldiers and selected others on Sunday. He did not deny Sabbathkeepers rest on the Sabbath.
Poor Constantine is the boogie man of Sabbath keepers, non-Trinitarians, and people who deny our canon of Scripture.
By the way, Samuele's findings were evidence Ellen G. White was a false prophetess, because she claimed a vision that the Pope changed the Sabbath. There wasn't even a Pope as we know it until many centuries later. There was a bishop of Rome, but he had no power like this. The idea of a Pope gradually developed over many centuries. It seems like wild-eyed cultists, including the cult leader I followed for a decade of my life, are totally ignorant of this fact.
But, then, I don't expect good church history from most Christians, let alone an ignorant cultist.