You address some critical points. Before the New Covenant we had types and shadows. Then Christ fulfilled those types and shadows. Why Christians want to use more types and shadows for the Real Christ, I don’t know.
Baptism represents something real. The real death and resurrection of Jesus Christ.
The Lord’s Supper represents His sacrifice for us. “Do this in remembrance.”
In the OT, the ceremonies and rituals looked ahead to fulfillment.
In the NT, baptism and communion look both back and forward representing in terms that humans can understand, spiritual realities that have occurred in the lives of the believers.