Symbology Options Removed in Basemap Layers

Hi everyone! I have a small question that seems particularly difficult for me to figure out.

If I add new data (any new data) to a new map, everything works fine. If I first create a new basemap layer and add data under that heirarchy, then most of my options in the Layer Properties dialog box vanish. The only tab I see is General - so I can't set symbology, selection data, source data, fields, etc.

If I move this layer back under the main heirarchy (i.e., under the main "Layers" level, equal to the "new basemap layer" I just created) then all of these options return.

I have tried this with a brand new map, a new basemap layer, and all kinds of shapefiles just to see if some particular something had a strange setting. It happens every time.

Has anyone else experienced this, and how did you fix it?

Thanks!

Austin