"could you provide a scripture where Jesus commanded that his death be observed"
You know the scriptures.
Luke 22:19 for one.
As for partaking. He said "Keep doing this in remembrance of me". The only ones who remember him are the disciples that heard him. That is none of us today. We don't partake because we don't have a memory of him. We know him by reading stories from a book. So to remember him, we reread the stories, not eat bread and drink wine.