Depreciated items should be shown differently on the contents page of AGOL so you don't have to click on it to know it has been depreciated.
I agree, a small red/green symbol would be suffice.
Looks like this was implemented with the December 2017 update see here:
What's new—ArcGIS Online Help | ArcGIS
able to mark something authoritative or deprecated is one thing, but there is no easy way to see that status from the content menu unless you open up the item details (many clicks later if you have many items in a folder you need to verify). OP (and myself) would like to see some sort of symbol next to the item (from the content menu) that would represent that status.
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