As with the law of Moses, there were community rules for living the law of Christ. In modern days, we understand that there is an organization known as a church, within which there are laws establishing how that community of believers is to be governed. That need was also present when the church and the community were essentially the same. Thus, there were laws laid down to define the boundaries of the community.
One of those was participation in the sacrament. It was to be done worthily, or as believers. The idea that it was to be done worthily must have meant that one was willing to obey the doctrine of Christ, which was repentance and baptism. It does not mean that those of us who might most need the sacrament to renew our covenants after repentance should not partake.