Any argument that Christians must keep any part of the Mosaic Law is just dishonest about the structure and implementation of the Old Testament law, and indicates a severe ignorance about its applications. There are 613 Commandments, all of which are equally important, and all of them must be kept. Or none of them. There is NO distinction in the Mosaic Law between "ritualistic" and "moral" law. Sabbattarian Christians conjure up that self-serving distinction purely out of convenience. They have picked a few of the 613 Commandments at random, based on the ones that happen to tickle their fancy. That is willfully dishonest to the intent of the Law.
If you were to approach an rabbinical expert on the Mosaic Law, and announce self-righteously that you are "keeping the Ten Commandments," they would look on you as though you are mentally deranged. Under Mosaic Law, there is no such a thing as the "Ten Commandments." What we know as the "Decalogue" is subsumed into the overall structure of the 613 Commandments. Judaism does not regard the ten commandments as anything particularly unique or special in relationship to the other 603 Commandments. They are merely ten among many other laws of equal importance.
Out of the mandatory 613 Mosaic laws, Sabbattarians pick and choose a tiny handful that happily coincide with their overall goals of preening self-righteousness over other Christians. They flatter themselves all too easily. If you understand the way the Mosaic law works, all they have merely done is make themselves looks bizarre and foolish. The Apostles repeatedly denounced such behavior as "Judaizing." The Apostles were experts on the Mosaic Law. Sabbattarians are not.
For Christians, Colossians 2:16-17 means what it says.
For Christians, the AD 50 Council of Jerusalem emphatically means what it says: Gentile Christians shall not be bound by the Mosaic law.
Any argument that the Sabbath is a memorial of Creation indicates an profound ignorance of the original Hebrew that both Genesis and Exodus were written in. The writer of the book of Genesis took great pains to make it clear that the Sabbath did not begin at the 7th day of Creation. Hebrew scholars have made that point absolutely clear. The Sabbath commandment was not given to the Children of Israel until at least a month after their delivery from Egyptian slavery. Meanwhile, they would have unintentionally broken the Sabbath at least four times during their crossing of the Sinai. There is absolutely no evidence whatsoever that anyone kept the Sabbath prior to Sinai. NONE!
Christians began worshiping on Sunday no later than 1 week after the Resurrection. Christ then Ascended on a Sunday. The Day of Pentecost, the Church's Birthday was on a Sunday. It would have been BIZARRE if the early Christians had continued to keep the Sabbath, given the impact those three events clearly would have had on them. Why were all the early Christians in one place on a Sunday when the Day of Pentecost took place? Because they had started doing so in honor of the Resurrection. By the Day of Pentecost, it was an entrenched Christian custom already.
The argument for keeping just one pet commandment out of the 613 of the Mosaic Law simply denigrates the obvious meaning of the crucifixion, the Resurrection, the Ascension and the Day of Pentecost. It is a Salvation by Works theory of "Partial Atonement." It is an argument that one must keep the entirety of the Mosaic Law, because Christ's sacrifice is not enough. Fortunately for Christians, even Christians who keep the Sabbath aren't even CLOSE to meeting that burden.
If you want to keep the Sabbath and have some integrity, you need to go through the full-scale conversion process to Judaism that is mandatory, including circumcision. It is extremely highly-unlikely any Sabbattarian Christian would do that. For an unconverted Gentile to keep the Sabbath is such a serious offense against God, an observant Jew is required the impose of the Death Penalty. Christians who keep the Sabbath are as bizarre as if they suddenly developed a yen to sacrifice some animals in their backyard temple.