Hello @Marc_Graham ,
Thank you for using ArcGIS for AutoCAD!
As my colleague mentioned depending upon what organization you have connected will determine what items are available but also I might for ArcGIS Enterprise it could differ with what version. I really appreciate the provided screen captures. The bottom one appears to be connected to ArcGIS Enterprise based on its name in the sidebar.
Here is ArcGIS Online without signing in:
Here is ArcGIS Enterprise 11.3: