Some layer types can only be on top of other layers in a web map, others only below. Overall, I have no control on where they draw in the stack, depending on the "type" of layer they are.
This does not work for adequate cartographic display of GIS data and is a major flaw in the rendering capabilities of AGOL web maps. It is critical that layers can be moved to the appropriate drawing location so that spatial information can be communicated effectively.
Please enable me to order my layers as needed.