That God plans the end of a story, especially that He planned the eternal life of the sheep, does not mean that He did not plan to use means to get the sheep eternal life. As an author, just because He knows the last page, that does not require Him to write only the last page.
God did not only plan that the sheep would never perish, He planned that they would never perish by the death and resurrection of the Shepherd in place of the sheep. God did not only plan that the sheep would follow the Shepherd, He planned when and where He would call them and open their ears to believe and follow. God ordains the destination and the route, the vehicle, the weather conditions, and who will ride shotgun.
As He planned our eternal life He ordained our time at the Lord’s Table. Why this ordinance? It is a meal to the end. He does not plan for us to work without giving us food. He does not plan for us to be brave without increasing our confidence that we have peace with Him. He does not plan for our witness without giving us a platform: “as often as we eat the bread and drink the cup we proclaim the Lord’s death until He comes.”
We shouldn’t play with communion because it is too powerful. God feeds us, unites us, and secures our steps as certainly as He knows our end.