I don't think your grain of salt theory is a good one to apply to learning what has happened to Christianity. The bottom line for Christians is scripture. It is idol worship, the worship of the sun as a God that historically started worship on the day labeled of the sun or Sunday and scripture the started worship on the day later labeled for Saturn, or Saturday. that it is scripture to worship on the seventh day of the week.
Christians don't worship the Sun. This is ludicrous as saying that Sabbath observers worship Saturn. And, the requirement to observe the Sabbath is not in effect since the Mosaic Covenant is not in effect. See Acts 15, Gal 3-4, Rom 7:1-6, Eph 2:13-15, Heb 7,8, Col 2:16-17.
Christians meet on the first day of the week because of the resurrection. Jesus rose from the grave on the first day of the week. His resurrection body is the beginning of the new creation. Christians are participating in the "age to come" now, in one sense, so they identify with their Lord and Savior by attending services on the eighth day. The eighth day is the first day of the new week.
This was foreshadowed through the use of the number "8" and "50" in Scripture. For instance, Hebrew babies were circumcised on the eighth day, which is 7+1. This symbolizes a new creation, and was a foreshadow of regeneration through the Holy Spirit. The number "50", which is the same as (7x7)+1, is used in a similar manner. For instance, Pentecost was observed on the 50th day after the Sabbath within the Days of Unleavened Bread, and it relates to the beginning of a new humanity, possessing the Holy Spirit and in union with Christ.
Believers are not under the Mosaic economy, which is typified by 7. They are under the New Covenant, not the Old Covenant. They are participants of the age to come, and not the present evil age.
This transition began in the New Testament church. Jesus appeared on Sunday, and not on the Sabbath, after the Resurrection. Why, if it continues to be such an important day?
We meet with Jesus on the first day, just like the believers after the Resurrection.
By the way, here's a letter I wrote to a friend on this issue:
The number “8” has to do with the new creation, and so does the number “50”….which is (7X7) + 1.
Jesus worked 6 days (symbolically) in his ministry, and finished his work on the cross on Friday (“It is finished”) then rested in the grave on Saturday. He was resurrected on Sunday (day 8) as a new creation (in terms of his resurrection body; not in terms of being YHVH).
Jesus is the BEGINNING of the new creation; the firstfruits (I Corinthians 15, Revelation 3:1).
Hebrew children were physically circumcised on the 8th day, which is a physical type of the new birth or the new creation or being born again (Leviticus 12:3).
On the first Pentecost after the Exodus (which is calculated as the 50th day from the weekly Sabbath during Passover), the Israelites received the Law on Mount Sinai (by Jewish tradition), and became a new physical nation that typified the Church.
On the first Pentecost after the resurrection of Jesus, the Holy Spirit was received by the apostolic church, and the Church became a new spiritual nation; a kingdom of priests (Acts 2).
On the land sabbath year, at the end of the year, all debt was forgiven, and there is a new beginning starting in the eighth year (Deuteronomy 15:1-6). This is symbolic of Jesus and the forgiveness of our sins to begin a new life.
On the Jubilee year, which is the 50th year in the Israelite calendar system, all debts were forgiven and the land was returned back to the original property owners; in essence a new life and a restoration (Leviticus 25:8-15). For the believer, this relates to the liberation that we receive in Jesus, where our spiritual debt is forgiven.
So, these things point toward the new creation, which starts with Jesus’ resurrection. For us, regeneration (being born again) is the beginning of our new life. Ultimately, the new creation reaches fulfillment in a New Heavens and New Earth/New Jerusalem (Revelation 21-22).
I believe this is the theological justification for the day of worship being on Sunday rather than the Jewish Sabbath. I am convinced that the early church had SOLID THEOLOGICAL REASONS for the practice.
Jesus our Lord, the Church, and each individual Christian, is a new creation.