I cannot believe this is still something not available, but here we go ---
Story: As a user, I want to upload a KMZ and have it appear on a map just like I can for a KML without having to convert it outside of ArcGIS Online or publish through ArcGIS Pro.
Justification: KMZs remain widely used and should be a geospatial file type available for use within ArcGIS Online for the maps and apps we create and manage.
