It was not called a sacrament or an ordinance nor were the disciples commanded to routinely celebrate the rite. Paul says it is optional with his “as oft as you eat this bread and drink this cup...”. . Look at the discussion that took place at the Last Supper after the breaking of bread. They were laying around drinking and eating and debating what their places of authority were going to be in the promised kingdom. It was an argument over who was going to be sitting next to Jesus in the seats of power in the kingdom that was to come; rank ambition. Jesus does not criticize them but points out they will eat and drink with Him in the Kingdom and be rulers over kingdoms appointed to them. He exposed a traitor who had participated in the brotherhood meal, and He deflated the braggadocio of Peter; all of these things after the breaking of bread. There was nothing sacred about the “breaking of bread” and definitely, no grace was bestowed at that time.
Look at how the Corinthian church was celebrating it. It followed the meal like the Last Supper did. It was a part of the fellowship that identified them as a unity in Christ and inheritors of the kingdom that was to come.
Berkhof defines sacrament as “a holy ordinance instituted by Christ, in which by sensible signs the grace of God in Christ, and the benefits of the covenant of grace are represented, sealed, and applied to believers, and these, in turn, give expression to their faith and allegiance to God.” Nowhere in the scriptures does it say that in either baptism or communion the “benefits of the covenant of grace are ........, sealed, and applied to believers”. Represented, yes, but not the sealed and applied. Communion was just a variation of a common brotherhood rite with an eschatological component.
I’m not sure about your history lesson, but the “Last Supper” and subsequent Lord’s Supper was the new covenant feast meal to replace the old covenant passover.
The imagery of Christ’s body and blood shed clearly are the antitype to the passover lamb. Christ is the true Lamb of God.
We eat and drink Christ spiritually when we partake of the elements. It is a sacrament of fellowship between Christ and His people (1 Cor. 10:16,17). It is what sets us apart really, spiritually from the world (1 Cor. 10:21).
The early disciples did routinely celebrate the sacrament. It seems a common occurrence with the gathering of believers in the book of Acts. The fellowships mention the breaking of bread (communion).