The normative response, based on the confessionally expressed conviction, is: if God summons us to worship him, and that on the First Day of the week, that’s obligatory. It’s the law of God, morally (the one-day-in-7 principle) and positively by a particular prescription.
That some worship on Saturday still is commendable this far (and no further): they obey their conscience, though it happens to be misinformed. “Whatsoever is not of faith is sin.” Better to commit to remembering the moral dictum, and fail in the positive prescription; than to ignore both.
A complicated analogy would relate to the matter of polygamy. It is morally wrong to be involved in sexual immorality, adultery or anything like it or prior to it. Thus far the moral law of the seventh commandment. Scripture does not solve for the departure from the norm of one-man/one-woman marriage for a lifetime by compelling divorce and separation from all but one of many wives. A man of many wives and concubines may not be an elder in Christ’s church; but he is not put outside of the church for failing the prescription (at least, not if those marriages were contracted before conversion). Reforming cultural aberrations takes time.